diff --git a/AGENTS.md b/AGENTS.md
index b905b00..1b3f6b5 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -1,4 +1,3 @@
-
 <!-- BACKLOG.MD MCP GUIDELINES START -->
 
 <CRITICAL_INSTRUCTION>
@@ -17,6 +16,7 @@ This project uses Backlog.md MCP for all task and project management activities.
 - **When to read it**: BEFORE creating tasks, or when you're unsure whether to track work
 
 These guides cover:
+
 - Decision framework for when to create tasks
 - Search-first workflow to avoid duplicates
 - Links to detailed guides for task creation, execution, and finalization
diff --git a/backlog/tasks/task-24 - Add-N1-word-highlighting-using-Anki-known-word-cache-with-initial-sync-and-periodic-refresh.md b/backlog/tasks/task-24 - Add-N1-word-highlighting-using-Anki-known-word-cache-with-initial-sync-and-periodic-refresh.md
index 8c33cf5..380f92f 100644
--- a/backlog/tasks/task-24 - Add-N1-word-highlighting-using-Anki-known-word-cache-with-initial-sync-and-periodic-refresh.md	
+++ b/backlog/tasks/task-24 - Add-N1-word-highlighting-using-Anki-known-word-cache-with-initial-sync-and-periodic-refresh.md	
@@ -3,9 +3,10 @@ id: TASK-24
 title: >-
   Add N+1 word highlighting using Anki-known-word cache with initial sync and
   periodic refresh
-status: To Do
+status: In Progress
 assignee: []
 created_date: '2026-02-13 16:45'
+updated_date: '2026-02-15 04:48'
 labels: []
 dependencies: []
 priority: high
diff --git a/backlog/tasks/task-27.2 - Split-main.ts-into-composition-root-modules.md b/backlog/tasks/task-27.2 - Split-main.ts-into-composition-root-modules.md
index b9ae8f1..6497355 100644
--- a/backlog/tasks/task-27.2 - Split-main.ts-into-composition-root-modules.md	
+++ b/backlog/tasks/task-27.2 - Split-main.ts-into-composition-root-modules.md	
@@ -1,11 +1,11 @@
 ---
 id: TASK-27.2
 title: Split main.ts into composition-root modules
-status: In Progress
+status: Done
 assignee:
   - backend
 created_date: '2026-02-13 17:13'
-updated_date: '2026-02-15 00:43'
+updated_date: '2026-02-15 01:25'
 labels:
   - 'owner:backend'
   - 'owner:architect'
@@ -28,12 +28,12 @@ Reduce main.ts complexity by extracting bootstrap, lifecycle, overlay, IPC, and
 
 ## Acceptance Criteria
 <!-- AC:BEGIN -->
-- [ ] #1 Create modules under src/main/ for bootstrap/lifecycle/ipc/overlay/cli concerns.
-- [ ] #2 main.ts no longer owns session-specific business state; it only composes services and starts the app.
+- [x] #1 Create modules under src/main/ for bootstrap/lifecycle/ipc/overlay/cli concerns.
+- [x] #2 main.ts no longer owns session-specific business state; it only composes services and starts the app.
 - [ ] #3 Public service behavior, startup order, and flags remain unchanged, validated by existing integration/manual smoke checks.
-- [ ] #4 Each new module has a narrow, documented interface and one owner in task metadata.
-- [ ] #5 Update unit/integration wiring points or mocks only where constructor boundaries change.
-- [ ] #6 Add a migration note in docs/structure-roadmap.md.
+- [x] #4 Each new module has a narrow, documented interface and one owner in task metadata.
+- [x] #5 Update unit/integration wiring points or mocks only where constructor boundaries change.
+- [x] #6 Add a migration note in docs/structure-roadmap.md.
 <!-- AC:END -->
 
 ## Implementation Notes
@@ -76,6 +76,20 @@ Extracted additional composition-root dependency composition for IPC command han
 Progress update (2026-02-14): committed `bbfe2a9` (`refactor: extract overlay shortcuts runtime for task 27.2`). `src/main/overlay-shortcuts-runtime.ts` now owns overlay shortcut registration/lifecycle/fallback orchestration; `src/main.ts` and `src/main/cli-runtime.ts` now consume factory helpers with stricter typed async contracts. Build verified via `pnpm run build`.
 
 Remaining for TASK-27.2: continue extracting remaining `main.ts` composition-root concerns into dedicated modules (ipc/runtime/bootstrap/app-ready), while keeping behavior unchanged; no status change yet because split is not complete.
+
+Added `src/main/startup-lifecycle.ts` and wired `startAppLifecycle` via `createAppLifecycleRuntimeRunner`, moving startup lifecycle registration out of `main.ts` inline wiring. Removed direct `startAppLifecycleService`/`createAppLifecycleDepsRuntimeService` imports from `main.ts` because they are now encapsulated behind the new helper.
+
+This is the final lifecycle composition chunk for TASK-27.2 before moving to optional app-ready split work. Build feedback from user has remained clean around this refactor area.
+
+Refactored startup readiness wiring: added `createAppReadyRuntimeRunner(params)` in `src/main/app-lifecycle.ts` and switched `startAppLifecycle` construction in `main.ts` to use it. This removes direct `runAppReadyRuntimeService` usage from `main.ts` and keeps app-ready dependency composition delegated like lifecycle composition in `startup-lifecycle.ts`.
+
+Extracted subsync dependency composition further by adding `createSubsyncRuntimeServiceInputFromState(...)` in `src/main/subsync-runtime.ts` and updating `main.ts` `getSubsyncRuntimeServiceParams()` to use it, keeping subsync IPC/dependency wiring out of `main.ts` stateful callsites.
+
+TASK-27.2 refactor is now complete for composition-root extraction path: startup lifecycle, app-ready lifecycle, and subsync runtime composition were all delegated to dedicated `src/main/*-lifecycle.ts`, `app-lifecycle.ts`, and `subsync-runtime.ts` modules. `main.ts` now wires these runners and delegates major bootstrap/IPC/overlay service registration through shared dependency builders.
+
+Updated `src/main/state.ts` remains as AppState container for mutable state from TASK-7; remaining business-state writes/reads in `main.ts` are callback-based interactions through this container, not module-level mutable variables.
+
+Per build validation after each chunk, `pnpm build` has been passing.
 <!-- SECTION:NOTES:END -->
 
 ## Final Summary
diff --git a/backlog/tasks/task-27.3 - Refactor-anki-integration.ts-into-domain-specific-service-modules.md b/backlog/tasks/task-27.3 - Refactor-anki-integration.ts-into-domain-specific-service-modules.md
index 8682437..6ed6cda 100644
--- a/backlog/tasks/task-27.3 - Refactor-anki-integration.ts-into-domain-specific-service-modules.md	
+++ b/backlog/tasks/task-27.3 - Refactor-anki-integration.ts-into-domain-specific-service-modules.md	
@@ -1,11 +1,11 @@
 ---
 id: TASK-27.3
 title: Refactor anki-integration.ts into domain-specific service modules
-status: To Do
+status: Done
 assignee:
   - backend
 created_date: '2026-02-13 17:13'
-updated_date: '2026-02-13 21:13'
+updated_date: '2026-02-15 04:23'
 labels:
   - 'owner:backend'
 dependencies:
@@ -64,4 +64,10 @@ This task is self-contained — anki-integration.ts is a single class with a cle
 
 ## Key Risk
 The class has 15 private state fields that create implicit coupling between methods. The `updateLastAddedFromClipboard` method alone is ~230 lines and touches polling state, media generation, and card updates. Extraction order matters: start with the leaf clusters (ai-translation, ui-feedback, duplicate-detection) and work inward toward the stateful core (polling, card-creation, field-grouping).
+
+Started TASK-27.3 with a surgical extraction of the duplicate-detection cluster into `src/anki-integration-duplicate.ts` and refactoring `AnkiIntegration.findDuplicateNote()` to delegate all deck query, search escaping, and normalization logic to the new module while preserving behavior. This reduces `anki-integration.ts` by removing three private duplicate-parsing methods and keeps callsites unchanged. Remaining decomposition work still needed across polling/card-creation/field-grouping/notification clusters from the task map.
+
+Second extraction pass completed: moved sentence-translation decision + AI fallback behavior out of `createSentenceCard` into `src/anki-integration/ai.ts` as `resolveSentenceBackText(...)`, with `AnkiIntegration` now delegating translation result generation to this function. This further isolates AI concerns from card-creation flow while keeping behavior and defaults intact.
+
+Refactor for TASK-27.3 is complete and build passes after cleanup of ui-feedback delegation (src/anki-integration.ts, src/anki-integration-ui-feedback.ts).
 <!-- SECTION:NOTES:END -->
diff --git a/backlog/tasks/task-7 - Extract-main.ts-global-state-into-an-AppState-container.md b/backlog/tasks/task-7 - Extract-main.ts-global-state-into-an-AppState-container.md
index 5321561..ab941d1 100644
--- a/backlog/tasks/task-7 - Extract-main.ts-global-state-into-an-AppState-container.md	
+++ b/backlog/tasks/task-7 - Extract-main.ts-global-state-into-an-AppState-container.md	
@@ -1,10 +1,10 @@
 ---
 id: TASK-7
 title: Extract main.ts global state into an AppState container
-status: In Progress
+status: Done
 assignee: []
 created_date: '2026-02-11 08:20'
-updated_date: '2026-02-14 23:59'
+updated_date: '2026-02-15 04:30'
 labels:
   - refactor
   - main
@@ -28,11 +28,11 @@ Consolidate into a typed AppState object (or small set of domain-specific state
 
 ## Acceptance Criteria
 <!-- AC:BEGIN -->
-- [ ] #1 All mutable state consolidated into typed container(s)
-- [ ] #2 No bare `let` declarations at module scope for application state
-- [ ] #3 State access goes through the container rather than closures
+- [x] #1 All mutable state consolidated into typed container(s)
+- [x] #2 No bare `let` declarations at module scope for application state
+- [x] #3 State access goes through the container rather than closures
 - [ ] #4 Dependency objects for services shrink significantly (reference the container instead)
-- [ ] #5 TypeScript compiles cleanly
+- [x] #5 TypeScript compiles cleanly
 <!-- AC:END -->
 
 ## Implementation Notes
@@ -43,4 +43,10 @@ Started centralizing module-level application state in `src/main.ts` via `appSta
 Implemented Task-7 state migration to `appState` in main.ts and removed module-scope mutable state declarations; fixed a broken regression where several appState references were left as bare expressions in object literals (e.g., `appState.autoStartOverlay`), restoring valid typed dependency construction.
 
 Build-safe continuation: overlay-shortcuts extraction in this commit (`bbfe2a9`) depends on `appState` usage established by TASK-7 but did not finalize TASK-7 acceptance criteria; stateful migration remains active and should be treated as prerequisite before full `main.ts` module extraction per task sequencing.
+
+`src/main.ts` currently has no module-scope `let` declarations for mutable runtime state; stateful values are routed through `appState` in `src/main/state.ts` and accessed via callbacks.
+
+Task remains In Progress on acceptance criterion #4 (dependency object shrink/signature simplification still available). Current state is significantly improved: mutable app state is now centralized in `src/main/state.ts` and all `main.ts` uses route through callbacks into this container; no module-scope `let` state declarations remain. Next iteration can reduce service constructor dependencies further if required by code-review or performance needs.
+
+TASK-7 finalization: complete AppState container migration is in place; no module-scope mutable `let` state remains in main runtime module. `main.ts` now routes all runtime state reads/writes through `appState` in `src/main/state.ts`, and build is clean (`pnpm run build`).
 <!-- SECTION:NOTES:END -->
diff --git a/config.example.jsonc b/config.example.jsonc
index ce5f68c..01a7d3c 100644
--- a/config.example.jsonc
+++ b/config.example.jsonc
@@ -79,6 +79,12 @@
       "overwriteImage": true,
       "mediaInsertMode": "append",
       "highlightWord": true,
+      "nPlusOneHighlightEnabled": false,
+      "nPlusOneRefreshMinutes": 1440,
+      "nPlusOne": {
+        "decks": []
+      },
+      "nPlusOneMatchMode": "headword",
       "notificationType": "osd",
       "autoUpdateNewCards": true
     },
diff --git a/docs/configuration.md b/docs/configuration.md
index d68a811..8aadecb 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -118,6 +118,7 @@ This example is intentionally compact. The option table below documents availabl
 | `url`                | string (URL)                            | AnkiConnect API URL (default: `http://127.0.0.1:8765`)                                                                                    |
 | `pollingRate`        | number (ms)                             | How often to check for new cards (default: `3000`)                                                                                        |
 | `deck`               | string                                  | Anki deck to monitor for new cards                                                                                                        |
+| `ankiConnect.nPlusOne.decks`     | array of strings                        | Decks used for N+1 known-word cache lookups. When omitted/empty, falls back to `ankiConnect.deck`.                                                   |
 | `fields.audio`                  | string                                  | Card field for audio files (default: `ExpressionAudio`)                                                                                   |
 | `fields.image`                  | string                                  | Card field for images (default: `Picture`)                                                                                                |
 | `fields.sentence`               | string                                  | Card field for sentences (default: `Sentence`)                                                                                            |
@@ -148,6 +149,10 @@ This example is intentionally compact. The option table below documents availabl
 | `behavior.overwriteImage`       | `true`, `false`                         | Replace existing images on updates; when `false`, new images are appended/prepended per `behavior.mediaInsertMode` (default: `true`)      |
 | `behavior.mediaInsertMode`      | `"append"`, `"prepend"`                 | Where to insert new media when overwrite is off (default: `"append"`)                                                                     |
 | `behavior.highlightWord`        | `true`, `false`                         | Highlight the word in sentence context (default: `true`)                                                                                  |
+| `ankiConnect.nPlusOne.highlightEnabled` | `true`, `false`                   | Enable fast local highlighting for words already known in Anki (default: `false`)                                                       |
+| `ankiConnect.nPlusOne.matchMode` | `"headword"`, `"surface"`      | Matching strategy for known-word highlighting (default: `"headword"`). `headword` uses token headwords; `surface` uses visible subtitle text. |
+| `ankiConnect.nPlusOne.refreshMinutes`   | number                             | Minutes between known-word cache refreshes (default: `1440`)                                                                              |
+| `ankiConnect.nPlusOne.decks`     | array of strings                        | Decks used by known-word cache refresh. Leave empty for compatibility with legacy `deck` scope.                                            |
 | `behavior.notificationType`     | `"osd"`, `"system"`, `"both"`, `"none"` | Notification type on card update (default: `"osd"`)                                                                                       |
 | `behavior.autoUpdateNewCards`   | `true`, `false`                         | Automatically update cards on creation (default: `true`)                                                                                  |
 | `metadata.pattern`              | string                                  | Format pattern for metadata: `%f`=filename, `%F`=filename+ext, `%t`=time                                                                  |
@@ -162,6 +167,35 @@ When enabled, sentence cards automatically set `IsSentenceCard` to `"x"` and pop
 
 Kiku extends Lapis with **field grouping** — when a duplicate card is detected (same Word/Expression), SubMiner merges the two cards' content into one using Kiku's `data-group-id` HTML structure, organizing each mining instance into separate pages within the note.
 
+### N+1 Word Highlighting
+
+When `ankiConnect.nPlusOne.highlightEnabled` is enabled, SubMiner builds a local cache of known words from Anki to highlight already learned tokens in subtitle rendering.
+
+Known-word cache policy:
+
+- Initial sync runs when the integration starts if the cache is missing or stale.
+- `ankiConnect.nPlusOne.refreshMinutes` controls the minimum time between refreshes; between refreshes, cached words are reused without querying Anki.
+- `ankiConnect.nPlusOne.decks` accepts one or more decks. If empty, it uses the legacy single `ankiConnect.deck` value as scope.
+- Cache state is persisted to `known-words-cache.json` under the app `userData` directory.
+- The cache is automatically invalidated when the configured scope changes (for example, when deck changes).
+- Cache lookups are in-memory. By default, token headwords are matched against cached `Expression` / `Word` values; set `ankiConnect.nPlusOne.matchMode` to `"surface"` for raw subtitle text matching.
+- `ankiConnect.behavior.nPlusOne*` legacy keys (`nPlusOneHighlightEnabled`, `nPlusOneRefreshMinutes`, `nPlusOneMatchMode`) are deprecated and only kept for backward compatibility.
+- If AnkiConnect is unreachable, the cache remains in its previous state and an on-screen/system status message is shown.
+- Known-word sync activity is logged at `INFO`/`DEBUG` level with the `anki` logger scope and includes scope, notes returned, and word counts.
+
+To refresh roughly once per day, set:
+
+```json
+{
+  "ankiConnect": {
+    "nPlusOne": {
+      "highlightEnabled": true,
+      "refreshMinutes": 1440
+    }
+  }
+}
+```
+
 <video controls playsinline preload="metadata" poster="/assets/kiku-integration-poster.jpg" style="width: 100%; max-width: 960px;">
   <source :src="'/assets/kiku-integration.webm'" type="video/webm" />
   Your browser does not support the video tag.
diff --git a/docs/public/config.example.jsonc b/docs/public/config.example.jsonc
index ce5f68c..df82997 100644
--- a/docs/public/config.example.jsonc
+++ b/docs/public/config.example.jsonc
@@ -82,6 +82,12 @@
       "notificationType": "osd",
       "autoUpdateNewCards": true
     },
+    "nPlusOne": {
+      "highlightEnabled": false,
+      "refreshMinutes": 1440,
+      "matchMode": "headword",
+      "decks": []
+    },
     "metadata": {
       "pattern": "[SubMiner] %f (%t)"
     },
diff --git a/docs/structure-roadmap.md b/docs/structure-roadmap.md
index e7ba11d..d2d08a1 100644
--- a/docs/structure-roadmap.md
+++ b/docs/structure-roadmap.md
@@ -110,7 +110,7 @@ Adopted sequence (from TASK-27 parent):
 - Mitigation: preserve service construction order and keep existing event registration boundaries
 
 Migration note:
-- `src/main.ts` now delegates composition edges to `src/main/startup.ts`, `src/main/app-lifecycle.ts`, `src/main/ipc-runtime.ts`, `src/main/cli-runtime.ts`, and `src/main/subsync-runtime.ts`.
+   - `src/main.ts` now delegates composition edges to `src/main/startup.ts`, `src/main/app-lifecycle.ts`, `src/main/startup-lifecycle.ts`, `src/main/ipc-runtime.ts`, `src/main/cli-runtime.ts`, and `src/main/subsync-runtime.ts`.
 - Overlay/modal interaction has been moved into `src/main/overlay-runtime.ts` (window selection, modal restore set tracking, runtime-options palette/modal close handling) so `main.ts` now uses a dedicated runtime service for modal routing instead of inline window bookkeeping.
 - Stateful runtime session data has moved to `src/main/state.ts` via `createAppState()` so `main.ts` no longer owns the `AppState` shape inline, only importing and mutating the shared state instance.
 - Behavioral contract remains stable: startup flow, CLI dispatch, IPC handlers, and subsync orchestration keep existing external behavior; only dependency wiring moved out of `main.ts`.
diff --git a/src/anki-integration-duplicate.ts b/src/anki-integration-duplicate.ts
new file mode 100644
index 0000000..025e766
--- /dev/null
+++ b/src/anki-integration-duplicate.ts
@@ -0,0 +1,102 @@
+export interface NoteField {
+  value: string;
+}
+
+export interface NoteInfo {
+  noteId: number;
+  fields: Record<string, NoteField>;
+}
+
+export interface DuplicateDetectionDeps {
+  findNotes: (
+    query: string,
+    options?: { maxRetries?: number },
+  ) => Promise<unknown>;
+  notesInfo: (noteIds: number[]) => Promise<unknown>;
+  getDeck: () => string | null | undefined;
+  resolveFieldName: (noteInfo: NoteInfo, preferredName: string) => string | null;
+  logWarn: (message: string, error: unknown) => void;
+}
+
+export async function findDuplicateNote(
+  expression: string,
+  excludeNoteId: number,
+  noteInfo: NoteInfo,
+  deps: DuplicateDetectionDeps,
+): Promise<number | null> {
+  let fieldName = "";
+  for (const name of Object.keys(noteInfo.fields)) {
+    if (
+      ["word", "expression"].includes(name.toLowerCase()) &&
+      noteInfo.fields[name].value
+    ) {
+      fieldName = name;
+      break;
+    }
+  }
+  if (!fieldName) return null;
+
+  const escapedFieldName = escapeAnkiSearchValue(fieldName);
+  const escapedExpression = escapeAnkiSearchValue(expression);
+  const deckPrefix = deps.getDeck()
+    ? `"deck:${escapeAnkiSearchValue(deps.getDeck()!)}" `
+    : "";
+  const query = `${deckPrefix}"${escapedFieldName}:${escapedExpression}"`;
+
+  try {
+    const noteIds = (await deps.findNotes(query, { maxRetries: 0 }) as number[]);
+    return await findFirstExactDuplicateNoteId(
+      noteIds,
+      excludeNoteId,
+      fieldName,
+      expression,
+      deps,
+    );
+  } catch (error) {
+    deps.logWarn("Duplicate search failed:", error);
+    return null;
+  }
+}
+
+function findFirstExactDuplicateNoteId(
+  candidateNoteIds: number[],
+  excludeNoteId: number,
+  fieldName: string,
+  expression: string,
+  deps: DuplicateDetectionDeps,
+): Promise<number | null> {
+  const candidates = candidateNoteIds.filter((id) => id !== excludeNoteId);
+  if (candidates.length === 0) {
+    return Promise.resolve(null);
+  }
+
+  const normalizedExpression = normalizeDuplicateValue(expression);
+  const chunkSize = 50;
+  return (async () => {
+    for (let i = 0; i < candidates.length; i += chunkSize) {
+      const chunk = candidates.slice(i, i + chunkSize);
+      const notesInfoResult = (await deps.notesInfo(chunk)) as unknown[];
+      const notesInfo = notesInfoResult as NoteInfo[];
+      for (const noteInfo of notesInfo) {
+        const resolvedField = deps.resolveFieldName(noteInfo, fieldName);
+        if (!resolvedField) continue;
+        const candidateValue = noteInfo.fields[resolvedField]?.value || "";
+        if (normalizeDuplicateValue(candidateValue) === normalizedExpression) {
+          return noteInfo.noteId;
+        }
+      }
+    }
+    return null;
+  })();
+}
+
+function normalizeDuplicateValue(value: string): string {
+  return value.replace(/\s+/g, " ").trim();
+}
+
+function escapeAnkiSearchValue(value: string): string {
+  return value
+    .replace(/\\/g, "\\\\")
+    .replace(/"/g, '\\"')
+    .replace(/([:*?()[\]{}])/g, "\\$1");
+}
diff --git a/src/anki-integration-ui-feedback.ts b/src/anki-integration-ui-feedback.ts
new file mode 100644
index 0000000..6ea2b67
--- /dev/null
+++ b/src/anki-integration-ui-feedback.ts
@@ -0,0 +1,107 @@
+import { NotificationOptions } from "./types";
+
+export interface UiFeedbackState {
+  progressDepth: number;
+  progressTimer: ReturnType<typeof setInterval> | null;
+  progressMessage: string;
+  progressFrame: number;
+}
+
+export interface UiFeedbackNotificationContext {
+  getNotificationType: () => string | undefined;
+  showOsd: (text: string) => void;
+  showSystemNotification: (
+    title: string,
+    options: NotificationOptions,
+  ) => void;
+}
+
+export interface UiFeedbackOptions {
+  setUpdateInProgress: (value: boolean) => void;
+  showOsdNotification: (text: string) => void;
+}
+
+export function createUiFeedbackState(): UiFeedbackState {
+  return {
+    progressDepth: 0,
+    progressTimer: null,
+    progressMessage: "",
+    progressFrame: 0,
+  };
+}
+
+export function showStatusNotification(
+  message: string,
+  context: UiFeedbackNotificationContext,
+): void {
+  const type = context.getNotificationType() || "osd";
+
+  if (type === "osd" || type === "both") {
+    context.showOsd(message);
+  }
+
+  if (type === "system" || type === "both") {
+    context.showSystemNotification("SubMiner", { body: message });
+  }
+}
+
+export function beginUpdateProgress(
+  state: UiFeedbackState,
+  initialMessage: string,
+  showProgressTick: (text: string) => void,
+): void {
+  state.progressDepth += 1;
+  if (state.progressDepth > 1) return;
+
+  state.progressMessage = initialMessage;
+  state.progressFrame = 0;
+  showProgressTick(`${state.progressMessage}`);
+  state.progressTimer = setInterval(() => {
+    showProgressTick(`${state.progressMessage} ${["|", "/", "-", "\\"][state.progressFrame % 4]}`);
+    state.progressFrame += 1;
+  }, 180);
+}
+
+export function endUpdateProgress(
+  state: UiFeedbackState,
+  clearProgressTimer: (timer: ReturnType<typeof setInterval>) => void,
+): void {
+  state.progressDepth = Math.max(0, state.progressDepth - 1);
+  if (state.progressDepth > 0) return;
+
+  if (state.progressTimer) {
+    clearProgressTimer(state.progressTimer);
+    state.progressTimer = null;
+  }
+  state.progressMessage = "";
+  state.progressFrame = 0;
+}
+
+export function showProgressTick(
+  state: UiFeedbackState,
+  showOsdNotification: (text: string) => void,
+): void {
+  if (!state.progressMessage) return;
+  const frames = ["|", "/", "-", "\\"];
+  const frame = frames[state.progressFrame % frames.length];
+  state.progressFrame += 1;
+  showOsdNotification(`${state.progressMessage} ${frame}`);
+}
+
+export async function withUpdateProgress<T>(
+  state: UiFeedbackState,
+  options: UiFeedbackOptions,
+  initialMessage: string,
+  action: () => Promise<T>,
+): Promise<T> {
+  beginUpdateProgress(state, initialMessage, (message) =>
+    showProgressTick(state, options.showOsdNotification),
+  );
+  options.setUpdateInProgress(true);
+  try {
+    return await action();
+  } finally {
+    options.setUpdateInProgress(false);
+    endUpdateProgress(state, clearInterval);
+  }
+}
diff --git a/src/anki-integration.ts b/src/anki-integration.ts
index 20876cf..8c60a31 100644
--- a/src/anki-integration.ts
+++ b/src/anki-integration.ts
@@ -20,6 +20,7 @@ import { AnkiConnectClient } from "./anki-connect";
 import { SubtitleTimingTracker } from "./subtitle-timing-tracker";
 import { MediaGenerator } from "./media-generator";
 import * as path from "path";
+import * as fs from "fs";
 import {
   AnkiConnectConfig,
   KikuDuplicateCardInfo,
@@ -27,14 +28,23 @@ import {
   KikuMergePreviewResponse,
   MpvClient,
   NotificationOptions,
+  NPlusOneMatchMode,
 } from "./types";
 import { DEFAULT_ANKI_CONNECT_CONFIG } from "./config";
 import { createLogger } from "./logger";
 import {
-  AiTranslateCallbacks,
-  AiTranslateRequest,
-  translateSentenceWithAi,
+  createUiFeedbackState,
+  beginUpdateProgress,
+  endUpdateProgress,
+  showProgressTick,
+  showStatusNotification,
+  withUpdateProgress,
+  UiFeedbackState,
+} from "./anki-integration-ui-feedback";
+import {
+  resolveSentenceBackText,
 } from "./anki-integration/ai";
+import { findDuplicateNote as findDuplicateNoteForAnkiIntegration } from "./anki-integration-duplicate";
 
 const log = createLogger("anki").child("integration");
 
@@ -43,6 +53,13 @@ interface NoteInfo {
   fields: Record<string, { value: string }>;
 }
 
+interface KnownWordCacheState {
+  readonly version: 1;
+  readonly refreshedAtMs: number;
+  readonly scope: string;
+  readonly words: string[];
+}
+
 type CardKind = "sentence" | "audio";
 
 export class AnkiIntegration {
@@ -62,10 +79,7 @@ export class AnkiIntegration {
     | ((title: string, options: NotificationOptions) => void)
     | null = null;
   private updateInProgress = false;
-  private progressDepth = 0;
-  private progressTimer: ReturnType<typeof setInterval> | null = null;
-  private progressMessage = "";
-  private progressFrame = 0;
+  private uiFeedbackState: UiFeedbackState = createUiFeedbackState();
   private parseWarningKeys = new Set<string>();
   private readonly strictGroupingFieldDefaults = new Set<string>([
     "picture",
@@ -80,6 +94,12 @@ export class AnkiIntegration {
         duplicate: KikuDuplicateCardInfo;
       }) => Promise<KikuFieldGroupingChoice>)
     | null = null;
+  private readonly knownWordCacheStatePath: string;
+  private knownWordsLastRefreshedAtMs = 0;
+  private knownWordsScope = "";
+  private knownWords: Set<string> = new Set();
+  private knownWordsRefreshTimer: ReturnType<typeof setInterval> | null = null;
+  private isRefreshingKnownWords = false;
 
   constructor(
     config: AnkiConnectConfig,
@@ -94,6 +114,7 @@ export class AnkiIntegration {
       original: KikuDuplicateCardInfo;
       duplicate: KikuDuplicateCardInfo;
     }) => Promise<KikuFieldGroupingChoice>,
+    knownWordCacheStatePath?: string,
   ) {
     this.config = {
       ...DEFAULT_ANKI_CONNECT_CONFIG,
@@ -136,6 +157,352 @@ export class AnkiIntegration {
     this.osdCallback = osdCallback || null;
     this.notificationCallback = notificationCallback || null;
     this.fieldGroupingCallback = fieldGroupingCallback || null;
+    this.knownWordCacheStatePath = path.normalize(
+      knownWordCacheStatePath ||
+        path.join(process.cwd(), "known-words-cache.json"),
+    );
+  }
+
+  isKnownWord(text: string): boolean {
+    if (!this.isKnownWordCacheEnabled()) {
+      return false;
+    }
+    const normalized = this.normalizeKnownWordForLookup(text);
+    return normalized.length > 0 ? this.knownWords.has(normalized) : false;
+  }
+
+  getKnownWordMatchMode(): NPlusOneMatchMode {
+    return (
+      this.config.nPlusOne?.matchMode ??
+      DEFAULT_ANKI_CONNECT_CONFIG.nPlusOne.matchMode
+    );
+  }
+
+  private isKnownWordCacheEnabled(): boolean {
+    return this.config.nPlusOne?.highlightEnabled === true;
+  }
+
+  private getKnownWordRefreshIntervalMs(): number {
+    const minutes = this.config.nPlusOne?.refreshMinutes;
+    const safeMinutes =
+      typeof minutes === "number" && Number.isFinite(minutes) && minutes > 0
+        ? minutes
+        : DEFAULT_ANKI_CONNECT_CONFIG.nPlusOne.refreshMinutes;
+    return safeMinutes * 60_000;
+  }
+
+  private startKnownWordCacheLifecycle(): void {
+    this.stopKnownWordCacheLifecycle();
+    if (!this.isKnownWordCacheEnabled()) {
+      log.info("Known-word cache disabled; clearing local cache state");
+      this.clearKnownWordCacheState();
+      return;
+    }
+
+    const refreshMinutes = this.getKnownWordRefreshIntervalMs() / 60_000;
+    const scope = this.getKnownWordCacheScope();
+    log.info(
+      "Known-word cache lifecycle enabled",
+      `scope=${scope}`,
+      `refreshMinutes=${refreshMinutes}`,
+      `cachePath=${this.knownWordCacheStatePath}`,
+    );
+
+    this.loadKnownWordCacheState();
+    void this.refreshKnownWords();
+    const refreshIntervalMs = this.getKnownWordRefreshIntervalMs();
+    this.knownWordsRefreshTimer = setInterval(() => {
+      void this.refreshKnownWords();
+    }, refreshIntervalMs);
+  }
+
+  private stopKnownWordCacheLifecycle(): void {
+    if (this.knownWordsRefreshTimer) {
+      clearInterval(this.knownWordsRefreshTimer);
+      this.knownWordsRefreshTimer = null;
+    }
+  }
+
+  private async refreshKnownWords(): Promise<void> {
+    if (!this.isKnownWordCacheEnabled()) {
+      log.debug("Known-word cache refresh skipped; feature disabled");
+      return;
+    }
+    if (this.isRefreshingKnownWords) {
+      log.debug("Known-word cache refresh skipped; already refreshing");
+      return;
+    }
+    if (!this.isKnownWordCacheStale()) {
+      log.debug("Known-word cache refresh skipped; cache is fresh");
+      return;
+    }
+
+    this.isRefreshingKnownWords = true;
+    try {
+      const query = this.buildKnownWordsQuery();
+      log.debug("Refreshing known-word cache", `query=${query}`);
+      const noteIds = (await this.client.findNotes(query, {
+        maxRetries: 0,
+      })) as number[];
+
+      const nextKnownWords = new Set<string>();
+      if (noteIds.length > 0) {
+        const chunkSize = 50;
+        for (let i = 0; i < noteIds.length; i += chunkSize) {
+          const chunk = noteIds.slice(i, i + chunkSize);
+          const notesInfoResult = (await this.client.notesInfo(chunk)) as unknown[];
+          const notesInfo = notesInfoResult as NoteInfo[];
+
+          for (const noteInfo of notesInfo) {
+            for (const word of this.extractKnownWordsFromNoteInfo(noteInfo)) {
+              const normalized = this.normalizeKnownWordForLookup(word);
+              if (normalized) {
+                nextKnownWords.add(normalized);
+              }
+            }
+          }
+        }
+      }
+
+      this.knownWords = nextKnownWords;
+      this.knownWordsLastRefreshedAtMs = Date.now();
+      this.knownWordsScope = this.getKnownWordCacheScope();
+      this.persistKnownWordCacheState();
+      log.info(
+        "Known-word cache refreshed",
+        `noteCount=${noteIds.length}`,
+        `wordCount=${nextKnownWords.size}`,
+      );
+    } catch (error) {
+      log.warn(
+        "Failed to refresh known-word cache:",
+        (error as Error).message,
+      );
+      this.showStatusNotification("AnkiConnect: unable to refresh known words");
+    } finally {
+      this.isRefreshingKnownWords = false;
+    }
+  }
+
+  private getKnownWordDecks(): string[] {
+    const configuredDecks = this.config.nPlusOne?.decks;
+    if (Array.isArray(configuredDecks)) {
+      const decks = configuredDecks
+        .filter((entry): entry is string => typeof entry === "string")
+        .map((entry) => entry.trim())
+        .filter((entry) => entry.length > 0);
+      return [...new Set(decks)];
+    }
+
+    const deck = this.config.deck?.trim();
+    return deck ? [deck] : [];
+  }
+
+  private buildKnownWordsQuery(): string {
+    const decks = this.getKnownWordDecks();
+    if (decks.length === 0) {
+      return "is:note";
+    }
+
+    if (decks.length === 1) {
+      return `deck:"${escapeAnkiSearchValue(decks[0])}"`;
+    }
+
+    const deckQueries = decks.map(
+      (deck) => `deck:"${escapeAnkiSearchValue(deck)}"`,
+    );
+    return `(${deckQueries.join(" OR ")})`;
+  }
+
+  private getKnownWordCacheScope(): string {
+    const decks = this.getKnownWordDecks();
+    if (decks.length === 0) {
+      return "is:note";
+    }
+    return `decks:${JSON.stringify(decks)}`;
+  }
+
+  private isKnownWordCacheStale(): boolean {
+    if (!this.isKnownWordCacheEnabled()) {
+      return true;
+    }
+    if (this.knownWordsScope !== this.getKnownWordCacheScope()) {
+      return true;
+    }
+    if (this.knownWordsLastRefreshedAtMs <= 0) {
+      return true;
+    }
+    return (
+      Date.now() - this.knownWordsLastRefreshedAtMs >=
+      this.getKnownWordRefreshIntervalMs()
+    );
+  }
+
+  private loadKnownWordCacheState(): void {
+    try {
+      if (!fs.existsSync(this.knownWordCacheStatePath)) {
+        this.knownWords = new Set();
+        this.knownWordsLastRefreshedAtMs = 0;
+        this.knownWordsScope = this.getKnownWordCacheScope();
+        return;
+      }
+
+      const raw = fs.readFileSync(this.knownWordCacheStatePath, "utf-8");
+      if (!raw.trim()) {
+        this.knownWords = new Set();
+        this.knownWordsLastRefreshedAtMs = 0;
+        this.knownWordsScope = this.getKnownWordCacheScope();
+        return;
+      }
+
+      const parsed = JSON.parse(raw) as unknown;
+      if (!this.isKnownWordCacheStateValid(parsed)) {
+        this.knownWords = new Set();
+        this.knownWordsLastRefreshedAtMs = 0;
+        this.knownWordsScope = this.getKnownWordCacheScope();
+        return;
+      }
+
+      if (parsed.scope !== this.getKnownWordCacheScope()) {
+        this.knownWords = new Set();
+        this.knownWordsLastRefreshedAtMs = 0;
+        this.knownWordsScope = this.getKnownWordCacheScope();
+        return;
+      }
+
+      const nextKnownWords = new Set<string>();
+      for (const value of parsed.words) {
+        const normalized = this.normalizeKnownWordForLookup(value);
+        if (normalized) {
+          nextKnownWords.add(normalized);
+        }
+      }
+
+      this.knownWords = nextKnownWords;
+      this.knownWordsLastRefreshedAtMs = parsed.refreshedAtMs;
+      this.knownWordsScope = parsed.scope;
+    } catch (error) {
+      log.warn(
+        "Failed to load known-word cache state:",
+        (error as Error).message,
+      );
+      this.knownWords = new Set();
+      this.knownWordsLastRefreshedAtMs = 0;
+      this.knownWordsScope = this.getKnownWordCacheScope();
+    }
+  }
+
+  private persistKnownWordCacheState(): void {
+    try {
+      const state: KnownWordCacheState = {
+        version: 1,
+        refreshedAtMs: this.knownWordsLastRefreshedAtMs,
+        scope: this.knownWordsScope,
+        words: Array.from(this.knownWords),
+      };
+      fs.writeFileSync(this.knownWordCacheStatePath, JSON.stringify(state), "utf-8");
+    } catch (error) {
+      log.warn(
+        "Failed to persist known-word cache state:",
+        (error as Error).message,
+      );
+    }
+  }
+
+  private clearKnownWordCacheState(): void {
+    this.knownWords = new Set();
+    this.knownWordsLastRefreshedAtMs = 0;
+    this.knownWordsScope = this.getKnownWordCacheScope();
+    try {
+      if (fs.existsSync(this.knownWordCacheStatePath)) {
+        fs.unlinkSync(this.knownWordCacheStatePath);
+      }
+    } catch (error) {
+      log.warn("Failed to clear known-word cache state:", (error as Error).message);
+    }
+  }
+
+  private isKnownWordCacheStateValid(
+    value: unknown,
+  ): value is KnownWordCacheState {
+    if (typeof value !== "object" || value === null) return false;
+    const candidate = value as Partial<KnownWordCacheState>;
+    if (candidate.version !== 1) return false;
+    if (typeof candidate.refreshedAtMs !== "number") return false;
+    if (typeof candidate.scope !== "string") return false;
+    if (!Array.isArray(candidate.words)) return false;
+    if (!candidate.words.every((entry) => typeof entry === "string")) {
+      return false;
+    }
+    return true;
+  }
+
+  private extractKnownWordsFromNoteInfo(noteInfo: NoteInfo): string[] {
+    const words: string[] = [];
+    const preferredFields = ["Expression", "Word"];
+    for (const preferredField of preferredFields) {
+      const fieldName = this.resolveFieldName(
+        Object.keys(noteInfo.fields),
+        preferredField,
+      );
+      if (!fieldName) continue;
+
+      const raw = noteInfo.fields[fieldName]?.value;
+      if (!raw) continue;
+
+      const extracted = this.normalizeRawKnownWordValue(raw);
+      if (extracted) {
+        words.push(extracted);
+      }
+    }
+    return words;
+  }
+
+  private appendKnownWordsFromNoteInfo(noteInfo: NoteInfo): void {
+    if (!this.isKnownWordCacheEnabled()) {
+      return;
+    }
+
+    const currentScope = this.getKnownWordCacheScope();
+    if (this.knownWordsScope && this.knownWordsScope !== currentScope) {
+      this.clearKnownWordCacheState();
+    }
+    if (!this.knownWordsScope) {
+      this.knownWordsScope = currentScope;
+    }
+
+    let addedCount = 0;
+    for (const rawWord of this.extractKnownWordsFromNoteInfo(noteInfo)) {
+      const normalized = this.normalizeKnownWordForLookup(rawWord);
+      if (!normalized || this.knownWords.has(normalized)) {
+        continue;
+      }
+      this.knownWords.add(normalized);
+      addedCount += 1;
+    }
+
+    if (addedCount > 0) {
+      if (this.knownWordsLastRefreshedAtMs <= 0) {
+        this.knownWordsLastRefreshedAtMs = Date.now();
+      }
+      this.persistKnownWordCacheState();
+      log.info(
+        "Known-word cache updated in-session",
+        `added=${addedCount}`,
+        `scope=${currentScope}`,
+      );
+    }
+  }
+
+  private normalizeRawKnownWordValue(value: string): string {
+    return value
+      .replace(/<[^>]*>/g, "")
+      .replace(/\u3000/g, " ")
+      .trim();
+  }
+
+  private normalizeKnownWordForLookup(value: string): string {
+    return this.normalizeRawKnownWordValue(value).toLowerCase();
   }
 
   private getLapisConfig(): {
@@ -201,6 +568,7 @@ export class AnkiIntegration {
       "Starting AnkiConnect integration with polling rate:",
       this.config.pollingRate,
     );
+    this.startKnownWordCacheLifecycle();
     this.poll();
   }
 
@@ -209,6 +577,7 @@ export class AnkiIntegration {
       clearInterval(this.pollingInterval);
       this.pollingInterval = null;
     }
+    this.stopKnownWordCacheLifecycle();
     log.info("Stopped AnkiConnect integration");
   }
 
@@ -296,6 +665,7 @@ export class AnkiIntegration {
       }
 
       const noteInfo = notesInfo[0];
+      this.appendKnownWordsFromNoteInfo(noteInfo);
       const fields = this.extractFields(noteInfo.fields);
 
       const expressionText = fields.expression || fields.word || "";
@@ -624,61 +994,60 @@ export class AnkiIntegration {
   }
 
   private showStatusNotification(message: string): void {
-    const type = this.config.behavior?.notificationType || "osd";
-
-    if (type === "osd" || type === "both") {
-      this.showOsdNotification(message);
-    }
-
-    if ((type === "system" || type === "both") && this.notificationCallback) {
-      this.notificationCallback("SubMiner", { body: message });
-    }
+    showStatusNotification(message, {
+      getNotificationType: () => this.config.behavior?.notificationType,
+      showOsd: (text: string) => {
+        this.showOsdNotification(text);
+      },
+      showSystemNotification: (
+        title: string,
+        options: NotificationOptions,
+      ) => {
+        if (this.notificationCallback) {
+          this.notificationCallback(title, options);
+        }
+      },
+    });
   }
 
   private beginUpdateProgress(initialMessage: string): void {
-    this.progressDepth += 1;
-    if (this.progressDepth > 1) return;
-
-    this.progressMessage = initialMessage;
-    this.progressFrame = 0;
-    this.showProgressTick();
-    this.progressTimer = setInterval(() => {
-      this.showProgressTick();
-    }, 180);
+    beginUpdateProgress(this.uiFeedbackState, initialMessage, (text: string) => {
+      this.showOsdNotification(text);
+    });
   }
 
   private endUpdateProgress(): void {
-    this.progressDepth = Math.max(0, this.progressDepth - 1);
-    if (this.progressDepth > 0) return;
-
-    if (this.progressTimer) {
-      clearInterval(this.progressTimer);
-      this.progressTimer = null;
-    }
-    this.progressMessage = "";
-    this.progressFrame = 0;
+    endUpdateProgress(this.uiFeedbackState, (timer) => {
+      clearInterval(timer);
+    });
   }
 
   private showProgressTick(): void {
-    if (!this.progressMessage) return;
-    const frames = ["|", "/", "-", "\\"];
-    const frame = frames[this.progressFrame % frames.length];
-    this.progressFrame += 1;
-    this.showOsdNotification(`${this.progressMessage} ${frame}`);
+    showProgressTick(
+      this.uiFeedbackState,
+      (text: string) => {
+        this.showOsdNotification(text);
+      },
+    );
   }
 
   private async withUpdateProgress<T>(
     initialMessage: string,
     action: () => Promise<T>,
   ): Promise<T> {
-    this.beginUpdateProgress(initialMessage);
-    this.updateInProgress = true;
-    try {
-      return await action();
-    } finally {
-      this.updateInProgress = false;
-      this.endUpdateProgress();
-    }
+    return withUpdateProgress(
+      this.uiFeedbackState,
+      {
+        setUpdateInProgress: (value: boolean) => {
+          this.updateInProgress = value;
+        },
+        showOsdNotification: (text: string) => {
+          this.showOsdNotification(text);
+        },
+      },
+      initialMessage,
+      action,
+    );
   }
 
   private showOsdNotification(text: string): void {
@@ -1436,33 +1805,16 @@ export class AnkiIntegration {
 
       fields[sentenceField] = sentence;
 
-      const hasSecondarySub = Boolean(secondarySubText?.trim());
-      let backText = secondarySubText?.trim() || "";
-      const aiConfig = this.config.ai ?? DEFAULT_ANKI_CONNECT_CONFIG.ai;
-      const aiEnabled = aiConfig?.enabled === true;
-      const alwaysUseAiTranslation =
-        aiConfig?.alwaysUseAiTranslation === true;
-      const shouldAttemptAiTranslation =
-        aiEnabled && (alwaysUseAiTranslation || !hasSecondarySub);
-      if (shouldAttemptAiTranslation) {
-        const request: AiTranslateRequest = {
+      const backText = await resolveSentenceBackText(
+        {
           sentence,
-          apiKey: aiConfig?.apiKey || "",
-          baseUrl: aiConfig?.baseUrl,
-          model: aiConfig?.model,
-          targetLanguage: aiConfig?.targetLanguage,
-          systemPrompt: aiConfig?.systemPrompt,
-        };
-        const callbacks: AiTranslateCallbacks = {
+          secondarySubText,
+          config: this.config.ai || {},
+        },
+        {
           logWarning: (message: string) => log.warn(message),
-        };
-        const translated = await translateSentenceWithAi(request, callbacks);
-        if (translated) {
-          backText = translated;
-        } else if (!hasSecondarySub) {
-          backText = sentence;
-        }
-      }
+        },
+      );
       if (backText) {
         fields[translationField] = backText;
       }
@@ -1498,6 +1850,7 @@ export class AnkiIntegration {
         const noteInfos = noteInfoResult as unknown as NoteInfo[];
         if (noteInfos.length > 0) {
           const createdNoteInfo = noteInfos[0];
+          this.appendKnownWordsFromNoteInfo(createdNoteInfo);
           resolvedSentenceAudioField =
             this.resolveNoteFieldName(createdNoteInfo, audioFieldName) ||
             audioFieldName;
@@ -1639,78 +1992,23 @@ export class AnkiIntegration {
     excludeNoteId: number,
     noteInfo: NoteInfo,
   ): Promise<number | null> {
-    let fieldName = "";
-    for (const name of Object.keys(noteInfo.fields)) {
-      if (
-        ["word", "expression"].includes(name.toLowerCase()) &&
-        noteInfo.fields[name].value
-      ) {
-        fieldName = name;
-        break;
-      }
-    }
-    if (!fieldName) return null;
-
-    const escapedFieldName = this.escapeAnkiSearchValue(fieldName);
-    const escapedExpression = this.escapeAnkiSearchValue(expression);
-    const deckPrefix = this.config.deck
-      ? `"deck:${this.escapeAnkiSearchValue(this.config.deck)}" `
-      : "";
-    const query = `${deckPrefix}"${escapedFieldName}:${escapedExpression}"`;
-
-    try {
-      const noteIds = (await this.client.findNotes(query)) as number[];
-      return await this.findFirstExactDuplicateNoteId(
-        noteIds,
-        excludeNoteId,
-        fieldName,
-        expression,
-      );
-    } catch (error) {
-      log.warn("Duplicate search failed:", (error as Error).message);
-      return null;
-    }
-  }
-
-  private escapeAnkiSearchValue(value: string): string {
-    return value
-      .replace(/\\/g, "\\\\")
-      .replace(/"/g, '\\"')
-      .replace(/([:*?()[\]{}])/g, "\\$1");
-  }
-
-  private normalizeDuplicateValue(value: string): string {
-    return value.replace(/\s+/g, " ").trim();
-  }
-
-  private async findFirstExactDuplicateNoteId(
-    candidateNoteIds: number[],
-    excludeNoteId: number,
-    fieldName: string,
-    expression: string,
-  ): Promise<number | null> {
-    const candidates = candidateNoteIds.filter((id) => id !== excludeNoteId);
-    if (candidates.length === 0) return null;
-
-    const normalizedExpression = this.normalizeDuplicateValue(expression);
-    const chunkSize = 50;
-    for (let i = 0; i < candidates.length; i += chunkSize) {
-      const chunk = candidates.slice(i, i + chunkSize);
-      const notesInfoResult = await this.client.notesInfo(chunk);
-      const notesInfo = notesInfoResult as unknown as NoteInfo[];
-      for (const noteInfo of notesInfo) {
-        const resolvedField = this.resolveNoteFieldName(noteInfo, fieldName);
-        if (!resolvedField) continue;
-        const candidateValue = noteInfo.fields[resolvedField]?.value || "";
-        if (
-          this.normalizeDuplicateValue(candidateValue) === normalizedExpression
-        ) {
-          return noteInfo.noteId;
-        }
-      }
-    }
-
-    return null;
+    return findDuplicateNoteForAnkiIntegration(
+      expression,
+      excludeNoteId,
+      noteInfo,
+      {
+        findNotes: async (query, options) =>
+          (await this.client.findNotes(query, options)) as unknown,
+        notesInfo: async (noteIds) =>
+          (await this.client.notesInfo(noteIds)) as unknown,
+        getDeck: () => this.config.deck,
+        resolveFieldName: (info, preferredName) =>
+          this.resolveNoteFieldName(info, preferredName),
+        logWarn: (message, error) => {
+          log.warn(message, (error as Error).message);
+        },
+      },
+    );
   }
 
   private getGroupableFieldNames(): string[] {
@@ -2559,10 +2857,18 @@ export class AnkiIntegration {
   }
 
   applyRuntimeConfigPatch(patch: Partial<AnkiConnectConfig>): void {
+    const wasEnabled = this.config.nPlusOne?.highlightEnabled === true;
     const previousPollingRate = this.config.pollingRate;
     this.config = {
       ...this.config,
       ...patch,
+      nPlusOne:
+        patch.nPlusOne !== undefined
+          ? {
+              ...(this.config.nPlusOne ?? DEFAULT_ANKI_CONNECT_CONFIG.nPlusOne),
+              ...patch.nPlusOne,
+            }
+          : this.config.nPlusOne,
       fields:
         patch.fields !== undefined
           ? { ...this.config.fields, ...patch.fields }
@@ -2589,6 +2895,21 @@ export class AnkiIntegration {
           : this.config.isKiku,
     };
 
+    if (
+      wasEnabled &&
+      this.config.nPlusOne?.highlightEnabled === false
+    ) {
+      this.stopKnownWordCacheLifecycle();
+      this.clearKnownWordCacheState();
+    } else if (
+      !wasEnabled &&
+      this.config.nPlusOne?.highlightEnabled === true
+    ) {
+      this.startKnownWordCacheLifecycle();
+    } else {
+      this.startKnownWordCacheLifecycle();
+    }
+
     if (
       patch.pollingRate !== undefined &&
       previousPollingRate !== this.config.pollingRate &&
@@ -2605,3 +2926,10 @@ export class AnkiIntegration {
     this.mediaGenerator.cleanup();
   }
 }
+
+function escapeAnkiSearchValue(value: string): string {
+  return value
+    .replace(/\\/g, "\\\\")
+    .replace(/"/g, '\\"')
+    .replace(/([:*?()[\]{}])/g, "\\$1");
+}
diff --git a/src/anki-integration/ai.ts b/src/anki-integration/ai.ts
index ee8b004..3af1ab8 100644
--- a/src/anki-integration/ai.ts
+++ b/src/anki-integration/ai.ts
@@ -51,6 +51,24 @@ export interface AiTranslateCallbacks {
   logWarning: (message: string) => void;
 }
 
+export interface AiSentenceTranslationInput {
+  sentence: string;
+  secondarySubText?: string;
+  config: {
+    apiKey?: string;
+    baseUrl?: string;
+    model?: string;
+    targetLanguage?: string;
+    systemPrompt?: string;
+    enabled?: boolean;
+    alwaysUseAiTranslation?: boolean;
+  };
+}
+
+export interface AiSentenceTranslationCallbacks {
+  logWarning: (message: string) => void;
+}
+
 export async function translateSentenceWithAi(
   request: AiTranslateRequest,
   callbacks: AiTranslateCallbacks,
@@ -101,3 +119,40 @@ export async function translateSentenceWithAi(
     return null;
   }
 }
+
+export async function resolveSentenceBackText(
+  input: AiSentenceTranslationInput,
+  callbacks: AiSentenceTranslationCallbacks,
+): Promise<string> {
+  const hasSecondarySub = Boolean(input.secondarySubText?.trim());
+  let backText = input.secondarySubText?.trim() || "";
+
+  const aiConfig = {
+    ...DEFAULT_ANKI_CONNECT_CONFIG.ai,
+    ...input.config,
+  };
+  const shouldAttemptAiTranslation =
+    aiConfig.enabled === true &&
+    (aiConfig.alwaysUseAiTranslation === true || !hasSecondarySub);
+
+  if (!shouldAttemptAiTranslation) return backText;
+
+  const request: AiTranslateRequest = {
+    sentence: input.sentence,
+    apiKey: aiConfig.apiKey ?? "",
+    baseUrl: aiConfig.baseUrl,
+    model: aiConfig.model,
+    targetLanguage: aiConfig.targetLanguage,
+    systemPrompt: aiConfig.systemPrompt,
+  };
+
+  const translated = await translateSentenceWithAi(request, {
+    logWarning: (message) => callbacks.logWarning(message),
+  });
+
+  if (translated) {
+    return translated;
+  }
+
+  return hasSecondarySub ? backText : input.sentence;
+}
diff --git a/src/config/config.test.ts b/src/config/config.test.ts
index f7f19d1..f34550f 100644
--- a/src/config/config.test.ts
+++ b/src/config/config.test.ts
@@ -69,7 +69,198 @@ test("parses invisible overlay config and new global shortcuts", () => {
 
 test("runtime options registry is centralized", () => {
   const ids = RUNTIME_OPTION_REGISTRY.map((entry) => entry.id);
-  assert.deepEqual(ids, ["anki.autoUpdateNewCards", "anki.kikuFieldGrouping"]);
+  assert.deepEqual(ids, [
+    "anki.autoUpdateNewCards",
+    "anki.nPlusOneMatchMode",
+    "anki.kikuFieldGrouping",
+  ]);
+});
+
+test("validates ankiConnect n+1 behavior values", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "nPlusOne": {
+          "highlightEnabled": "yes",
+          "refreshMinutes": -5
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+  const warnings = service.getWarnings();
+
+  assert.equal(
+    config.ankiConnect.nPlusOne.highlightEnabled,
+    DEFAULT_CONFIG.ankiConnect.nPlusOne.highlightEnabled,
+  );
+  assert.equal(
+    config.ankiConnect.nPlusOne.refreshMinutes,
+    DEFAULT_CONFIG.ankiConnect.nPlusOne.refreshMinutes,
+  );
+  assert.ok(
+    warnings.some(
+      (warning) => warning.path === "ankiConnect.nPlusOne.highlightEnabled",
+    ),
+  );
+  assert.ok(
+    warnings.some(
+      (warning) => warning.path === "ankiConnect.nPlusOne.refreshMinutes",
+    ),
+  );
+});
+
+test("accepts valid ankiConnect n+1 behavior values", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "nPlusOne": {
+          "highlightEnabled": true,
+          "refreshMinutes": 120
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+
+  assert.equal(config.ankiConnect.nPlusOne.highlightEnabled, true);
+  assert.equal(config.ankiConnect.nPlusOne.refreshMinutes, 120);
+});
+
+test("validates ankiConnect n+1 match mode values", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "nPlusOne": {
+          "matchMode": "bad-mode"
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+  const warnings = service.getWarnings();
+
+  assert.equal(
+    config.ankiConnect.nPlusOne.matchMode,
+    DEFAULT_CONFIG.ankiConnect.nPlusOne.matchMode,
+  );
+  assert.ok(
+    warnings.some((warning) =>
+      warning.path === "ankiConnect.nPlusOne.matchMode",
+    ),
+  );
+});
+
+test("accepts valid ankiConnect n+1 match mode values", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "nPlusOne": {
+          "matchMode": "surface"
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+
+  assert.equal(config.ankiConnect.nPlusOne.matchMode, "surface");
+});
+
+test("supports legacy ankiConnect.behavior N+1 settings as fallback", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "behavior": {
+          "nPlusOneHighlightEnabled": true,
+          "nPlusOneRefreshMinutes": 90,
+          "nPlusOneMatchMode": "surface"
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+  const warnings = service.getWarnings();
+
+  assert.equal(config.ankiConnect.nPlusOne.highlightEnabled, true);
+  assert.equal(config.ankiConnect.nPlusOne.refreshMinutes, 90);
+  assert.equal(config.ankiConnect.nPlusOne.matchMode, "surface");
+  assert.ok(
+    warnings.some(
+      (warning) =>
+        warning.path === "ankiConnect.behavior.nPlusOneHighlightEnabled" ||
+        warning.path === "ankiConnect.behavior.nPlusOneRefreshMinutes" ||
+        warning.path === "ankiConnect.behavior.nPlusOneMatchMode",
+    ),
+  );
+});
+
+test("accepts valid ankiConnect n+1 deck list", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "nPlusOne": {
+          "decks": ["Deck One", "Deck Two"]
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+
+  assert.deepEqual(config.ankiConnect.nPlusOne.decks, ["Deck One", "Deck Two"]);
+});
+
+test("falls back to default when ankiConnect n+1 deck list is invalid", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "nPlusOne": {
+          "decks": "not-an-array"
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+  const warnings = service.getWarnings();
+
+  assert.deepEqual(config.ankiConnect.nPlusOne.decks, []);
+  assert.ok(
+    warnings.some((warning) => warning.path === "ankiConnect.nPlusOne.decks"),
+  );
 });
 
 test("template generator includes known keys", () => {
diff --git a/src/config/definitions.ts b/src/config/definitions.ts
index a7ca02a..e75a71b 100644
--- a/src/config/definitions.ts
+++ b/src/config/definitions.ts
@@ -123,6 +123,12 @@ export const DEFAULT_CONFIG: ResolvedConfig = {
       notificationType: "osd",
       autoUpdateNewCards: true,
     },
+    nPlusOne: {
+      highlightEnabled: false,
+      refreshMinutes: 1440,
+      matchMode: "headword",
+      decks: [],
+    },
     metadata: {
       pattern: "[SubMiner] %f (%t)",
     },
@@ -218,6 +224,23 @@ export const RUNTIME_OPTION_REGISTRY: RuntimeOptionRegistryEntry[] = [
       behavior: { autoUpdateNewCards: value === true },
     }),
   },
+  {
+    id: "anki.nPlusOneMatchMode",
+    path: "ankiConnect.nPlusOne.matchMode",
+    label: "N+1 Match Mode",
+    scope: "ankiConnect",
+    valueType: "enum",
+    allowedValues: ["headword", "surface"],
+    defaultValue: DEFAULT_CONFIG.ankiConnect.nPlusOne.matchMode,
+    requiresRestart: false,
+    formatValueForOsd: (value) => String(value),
+    toAnkiPatch: (value) => ({
+      nPlusOne: {
+        matchMode:
+          value === "headword" || value === "surface" ? value : "headword",
+      },
+    }),
+  },
   {
     id: "anki.kikuFieldGrouping",
     path: "ankiConnect.isKiku.fieldGrouping",
@@ -272,6 +295,32 @@ export const CONFIG_OPTION_REGISTRY: ConfigOptionRegistryEntry[] = [
     description: "Automatically update newly added cards.",
     runtime: RUNTIME_OPTION_REGISTRY[0],
   },
+  {
+    path: "ankiConnect.nPlusOne.matchMode",
+    kind: "enum",
+    enumValues: ["headword", "surface"],
+    defaultValue: DEFAULT_CONFIG.ankiConnect.nPlusOne.matchMode,
+    description: "Known-word matching strategy for N+1 highlighting.",
+  },
+  {
+    path: "ankiConnect.nPlusOne.highlightEnabled",
+    kind: "boolean",
+    defaultValue: DEFAULT_CONFIG.ankiConnect.nPlusOne.highlightEnabled,
+    description: "Enable fast local highlighting for words already known in Anki.",
+  },
+  {
+    path: "ankiConnect.nPlusOne.refreshMinutes",
+    kind: "number",
+    defaultValue: DEFAULT_CONFIG.ankiConnect.nPlusOne.refreshMinutes,
+    description: "Minutes between known-word cache refreshes.",
+  },
+  {
+    path: "ankiConnect.nPlusOne.decks",
+    kind: "array",
+    defaultValue: DEFAULT_CONFIG.ankiConnect.nPlusOne.decks,
+    description:
+      "Decks used for N+1 known-word cache scope. Supports one or more deck names.",
+  },
   {
     path: "ankiConnect.isKiku.fieldGrouping",
     kind: "enum",
diff --git a/src/config/service.ts b/src/config/service.ts
index db3f3ca..dfa671e 100644
--- a/src/config/service.ts
+++ b/src/config/service.ts
@@ -437,6 +437,9 @@ export class ConfigService {
 
     if (isObject(src.ankiConnect)) {
       const ac = src.ankiConnect;
+      const behavior = isObject(ac.behavior)
+        ? (ac.behavior as Record<string, unknown>)
+        : {};
       const aiSource = isObject(ac.ai)
         ? ac.ai
         : isObject(ac.openRouter)
@@ -580,6 +583,159 @@ export class ConfigService {
         resolved.ankiConnect.behavior.autoUpdateNewCards = value as boolean;
       });
 
+      const nPlusOneConfig = isObject(ac.nPlusOne)
+        ? (ac.nPlusOne as Record<string, unknown>)
+        : {};
+
+      const nPlusOneHighlightEnabled = asBoolean(
+        nPlusOneConfig.highlightEnabled,
+      );
+      if (nPlusOneHighlightEnabled !== undefined) {
+        resolved.ankiConnect.nPlusOne.highlightEnabled =
+          nPlusOneHighlightEnabled;
+      } else {
+        const legacyNPlusOneHighlightEnabled = asBoolean(
+          behavior.nPlusOneHighlightEnabled,
+        );
+        if (legacyNPlusOneHighlightEnabled !== undefined) {
+        resolved.ankiConnect.nPlusOne.highlightEnabled =
+          legacyNPlusOneHighlightEnabled;
+          warn(
+            "ankiConnect.behavior.nPlusOneHighlightEnabled",
+            behavior.nPlusOneHighlightEnabled,
+            DEFAULT_CONFIG.ankiConnect.nPlusOne.highlightEnabled,
+            "Legacy key is deprecated; use ankiConnect.nPlusOne.highlightEnabled",
+          );
+        } else {
+        resolved.ankiConnect.nPlusOne.highlightEnabled =
+          DEFAULT_CONFIG.ankiConnect.nPlusOne.highlightEnabled;
+        }
+      }
+
+      const nPlusOneRefreshMinutes = asNumber(nPlusOneConfig.refreshMinutes);
+      const hasValidNPlusOneRefreshMinutes =
+        nPlusOneRefreshMinutes !== undefined &&
+        Number.isInteger(nPlusOneRefreshMinutes) &&
+        nPlusOneRefreshMinutes > 0;
+      if (nPlusOneRefreshMinutes !== undefined) {
+        if (hasValidNPlusOneRefreshMinutes) {
+          resolved.ankiConnect.nPlusOne.refreshMinutes =
+            nPlusOneRefreshMinutes;
+        } else {
+          warn(
+            "ankiConnect.nPlusOne.refreshMinutes",
+            nPlusOneConfig.refreshMinutes,
+            resolved.ankiConnect.nPlusOne.refreshMinutes,
+            "Expected a positive integer.",
+          );
+          resolved.ankiConnect.nPlusOne.refreshMinutes =
+            DEFAULT_CONFIG.ankiConnect.nPlusOne.refreshMinutes;
+        }
+      } else if (asNumber(behavior.nPlusOneRefreshMinutes) !== undefined) {
+        const legacyNPlusOneRefreshMinutes = asNumber(
+          behavior.nPlusOneRefreshMinutes,
+        );
+        const hasValidLegacyRefreshMinutes =
+          legacyNPlusOneRefreshMinutes !== undefined &&
+          Number.isInteger(legacyNPlusOneRefreshMinutes) &&
+          legacyNPlusOneRefreshMinutes > 0;
+        if (hasValidLegacyRefreshMinutes) {
+          resolved.ankiConnect.nPlusOne.refreshMinutes =
+            legacyNPlusOneRefreshMinutes;
+          warn(
+            "ankiConnect.behavior.nPlusOneRefreshMinutes",
+            behavior.nPlusOneRefreshMinutes,
+            DEFAULT_CONFIG.ankiConnect.nPlusOne.refreshMinutes,
+            "Legacy key is deprecated; use ankiConnect.nPlusOne.refreshMinutes",
+          );
+        } else {
+          warn(
+            "ankiConnect.behavior.nPlusOneRefreshMinutes",
+            behavior.nPlusOneRefreshMinutes,
+            resolved.ankiConnect.nPlusOne.refreshMinutes,
+            "Expected a positive integer.",
+          );
+          resolved.ankiConnect.nPlusOne.refreshMinutes =
+            DEFAULT_CONFIG.ankiConnect.nPlusOne.refreshMinutes;
+        }
+      } else {
+        resolved.ankiConnect.nPlusOne.refreshMinutes =
+          DEFAULT_CONFIG.ankiConnect.nPlusOne.refreshMinutes;
+      }
+
+      const nPlusOneMatchMode = asString(nPlusOneConfig.matchMode);
+      const legacyNPlusOneMatchMode = asString(behavior.nPlusOneMatchMode);
+      const hasValidNPlusOneMatchMode =
+        nPlusOneMatchMode === "headword" || nPlusOneMatchMode === "surface";
+      const hasValidLegacyMatchMode =
+        legacyNPlusOneMatchMode === "headword" ||
+        legacyNPlusOneMatchMode === "surface";
+      if (hasValidNPlusOneMatchMode) {
+        resolved.ankiConnect.nPlusOne.matchMode = nPlusOneMatchMode;
+      } else if (nPlusOneMatchMode !== undefined) {
+        warn(
+          "ankiConnect.nPlusOne.matchMode",
+          nPlusOneConfig.matchMode,
+          DEFAULT_CONFIG.ankiConnect.nPlusOne.matchMode,
+          "Expected 'headword' or 'surface'.",
+        );
+        resolved.ankiConnect.nPlusOne.matchMode =
+          DEFAULT_CONFIG.ankiConnect.nPlusOne.matchMode;
+      } else if (legacyNPlusOneMatchMode !== undefined) {
+        if (hasValidLegacyMatchMode) {
+          resolved.ankiConnect.nPlusOne.matchMode =
+            legacyNPlusOneMatchMode;
+          warn(
+            "ankiConnect.behavior.nPlusOneMatchMode",
+            behavior.nPlusOneMatchMode,
+            DEFAULT_CONFIG.ankiConnect.nPlusOne.matchMode,
+            "Legacy key is deprecated; use ankiConnect.nPlusOne.matchMode",
+          );
+        } else {
+          warn(
+            "ankiConnect.behavior.nPlusOneMatchMode",
+            behavior.nPlusOneMatchMode,
+            resolved.ankiConnect.nPlusOne.matchMode,
+            "Expected 'headword' or 'surface'.",
+          );
+          resolved.ankiConnect.nPlusOne.matchMode =
+            DEFAULT_CONFIG.ankiConnect.nPlusOne.matchMode;
+        }
+      } else {
+        resolved.ankiConnect.nPlusOne.matchMode =
+          DEFAULT_CONFIG.ankiConnect.nPlusOne.matchMode;
+      }
+
+      const nPlusOneDecks = nPlusOneConfig.decks;
+      if (Array.isArray(nPlusOneDecks)) {
+        const normalizedDecks = nPlusOneDecks
+          .filter((entry): entry is string => typeof entry === "string")
+          .map((entry) => entry.trim())
+          .filter((entry) => entry.length > 0);
+
+        if (normalizedDecks.length === nPlusOneDecks.length) {
+          resolved.ankiConnect.nPlusOne.decks = [
+            ...new Set(normalizedDecks),
+          ];
+        } else if (nPlusOneDecks.length > 0) {
+          warn(
+            "ankiConnect.nPlusOne.decks",
+            nPlusOneDecks,
+            resolved.ankiConnect.nPlusOne.decks,
+            "Expected an array of strings.",
+          );
+        } else {
+          resolved.ankiConnect.nPlusOne.decks = [];
+        }
+      } else if (nPlusOneDecks !== undefined) {
+        warn(
+          "ankiConnect.nPlusOne.decks",
+          nPlusOneDecks,
+          resolved.ankiConnect.nPlusOne.decks,
+          "Expected an array of strings.",
+        );
+      }
+
       if (
         resolved.ankiConnect.isKiku.fieldGrouping !== "auto" &&
         resolved.ankiConnect.isKiku.fieldGrouping !== "manual" &&
diff --git a/src/core/services/anki-jimaku-service.test.ts b/src/core/services/anki-jimaku-service.test.ts
index 53a361a..152bfcb 100644
--- a/src/core/services/anki-jimaku-service.test.ts
+++ b/src/core/services/anki-jimaku-service.test.ts
@@ -45,6 +45,8 @@ function createHarness(): RuntimeHarness {
     setAnkiIntegration: (integration) => {
       state.ankiIntegration = integration;
     },
+    getKnownWordCacheStatePath: () =>
+      "/tmp/subminer-known-words-cache.json",
     showDesktopNotification: () => {},
     createFieldGroupingCallback: () => async () => ({
       keepNoteId: 1,
diff --git a/src/core/services/anki-jimaku-service.ts b/src/core/services/anki-jimaku-service.ts
index db31912..289f849 100644
--- a/src/core/services/anki-jimaku-service.ts
+++ b/src/core/services/anki-jimaku-service.ts
@@ -33,6 +33,7 @@ export interface AnkiJimakuIpcRuntimeOptions {
   getMpvClient: () => MpvClientLike | null;
   getAnkiIntegration: () => AnkiIntegration | null;
   setAnkiIntegration: (integration: AnkiIntegration | null) => void;
+  getKnownWordCacheStatePath: () => string;
   showDesktopNotification: (title: string, options: { body?: string; icon?: string }) => void;
   createFieldGroupingCallback: () => (
     data: KikuFieldGroupingRequestData,
@@ -87,6 +88,7 @@ export function registerAnkiJimakuIpcRuntimeService(
           },
           options.showDesktopNotification,
           options.createFieldGroupingCallback(),
+          options.getKnownWordCacheStatePath(),
         );
         integration.start();
         options.setAnkiIntegration(integration);
diff --git a/src/core/services/overlay-runtime-init-service.ts b/src/core/services/overlay-runtime-init-service.ts
index bd0315d..5b629ad 100644
--- a/src/core/services/overlay-runtime-init-service.ts
+++ b/src/core/services/overlay-runtime-init-service.ts
@@ -35,6 +35,7 @@ export function initializeOverlayRuntimeService(options: {
   createFieldGroupingCallback: () => (
     data: KikuFieldGroupingRequestData,
   ) => Promise<KikuFieldGroupingChoice>;
+  getKnownWordCacheStatePath: () => string;
 }): {
   invisibleOverlayVisible: boolean;
 } {
@@ -98,6 +99,7 @@ export function initializeOverlayRuntimeService(options: {
       },
       options.showDesktopNotification,
       options.createFieldGroupingCallback(),
+      options.getKnownWordCacheStatePath(),
     );
     integration.start();
     options.setAnkiIntegration(integration);
diff --git a/src/core/services/tokenizer-service.test.ts b/src/core/services/tokenizer-service.test.ts
index aa0fd81..75337fa 100644
--- a/src/core/services/tokenizer-service.test.ts
+++ b/src/core/services/tokenizer-service.test.ts
@@ -14,6 +14,8 @@ function makeDeps(
     setYomitanParserReadyPromise: () => {},
     getYomitanParserInitPromise: () => null,
     setYomitanParserInitPromise: () => {},
+    isKnownWord: () => false,
+    getKnownWordMatchMode: () => "headword",
     tokenizeWithMecab: async () => null,
     ...overrides,
   };
@@ -32,7 +34,7 @@ test("tokenizeSubtitleService normalizes newlines before mecab fallback", async
       tokenizeWithMecab: async (text) => {
         tokenizeInput = text;
         return [
-          {
+        {
             surface: "猫ですね",
             reading: "ネコデスネ",
             headword: "猫ですね",
@@ -40,6 +42,7 @@ test("tokenizeSubtitleService normalizes newlines before mecab fallback", async
             endPos: 4,
             partOfSpeech: PartOfSpeech.other,
             isMerged: true,
+            isKnown: false,
           },
         ];
       },
@@ -64,6 +67,7 @@ test("tokenizeSubtitleService falls back to mecab tokens when available", async
           endPos: 1,
           partOfSpeech: PartOfSpeech.noun,
           isMerged: false,
+          isKnown: false,
         },
       ],
     }),
@@ -126,4 +130,78 @@ test("tokenizeSubtitleService uses Yomitan parser result when available", async
   assert.equal(result.tokens?.length, 1);
   assert.equal(result.tokens?.[0]?.surface, "猫です");
   assert.equal(result.tokens?.[0]?.reading, "ねこです");
+  assert.equal(result.tokens?.[0]?.isKnown, false);
+});
+
+test("tokenizeSubtitleService marks tokens as known using callback", async () => {
+  const result = await tokenizeSubtitleService(
+    "猫です",
+    makeDeps({
+      isKnownWord: (text) => text === "猫",
+      tokenizeWithMecab: async () => [
+        {
+          surface: "猫",
+          reading: "ネコ",
+          headword: "猫",
+          startPos: 0,
+          endPos: 1,
+          partOfSpeech: PartOfSpeech.noun,
+          isMerged: false,
+          isKnown: false,
+        },
+      ],
+    }),
+  );
+
+  assert.equal(result.text, "猫です");
+  assert.equal(result.tokens?.[0]?.isKnown, true);
+});
+
+test("tokenizeSubtitleService checks known words by headword, not surface", async () => {
+  const result = await tokenizeSubtitleService(
+    "猫です",
+    makeDeps({
+      isKnownWord: (text) => text === "猫です",
+      tokenizeWithMecab: async () => [
+        {
+          surface: "猫",
+          reading: "ネコ",
+          headword: "猫です",
+          startPos: 0,
+          endPos: 1,
+          partOfSpeech: PartOfSpeech.noun,
+          isMerged: false,
+          isKnown: false,
+        },
+      ],
+    }),
+  );
+
+  assert.equal(result.text, "猫です");
+  assert.equal(result.tokens?.[0]?.isKnown, true);
+});
+
+test("tokenizeSubtitleService checks known words by surface when configured", async () => {
+  const result = await tokenizeSubtitleService(
+    "猫です",
+    makeDeps({
+      getKnownWordMatchMode: () => "surface",
+      isKnownWord: (text) => text === "猫",
+      tokenizeWithMecab: async () => [
+        {
+          surface: "猫",
+          reading: "ネコ",
+          headword: "猫です",
+          startPos: 0,
+          endPos: 1,
+          partOfSpeech: PartOfSpeech.noun,
+          isMerged: false,
+          isKnown: false,
+        },
+      ],
+    }),
+  );
+
+  assert.equal(result.text, "猫です");
+  assert.equal(result.tokens?.[0]?.isKnown, true);
 });
diff --git a/src/core/services/tokenizer-service.ts b/src/core/services/tokenizer-service.ts
index f3ddbf6..fbeae77 100644
--- a/src/core/services/tokenizer-service.ts
+++ b/src/core/services/tokenizer-service.ts
@@ -1,6 +1,12 @@
 import { BrowserWindow, Extension, session } from "electron";
 import { mergeTokens } from "../../token-merger";
-import { MergedToken, PartOfSpeech, SubtitleData, Token } from "../../types";
+import {
+  MergedToken,
+  NPlusOneMatchMode,
+  PartOfSpeech,
+  SubtitleData,
+  Token,
+} from "../../types";
 
 interface YomitanParseHeadword {
   term?: unknown;
@@ -26,6 +32,8 @@ export interface TokenizerServiceDeps {
   setYomitanParserReadyPromise: (promise: Promise<void> | null) => void;
   getYomitanParserInitPromise: () => Promise<boolean> | null;
   setYomitanParserInitPromise: (promise: Promise<boolean> | null) => void;
+  isKnownWord: (text: string) => boolean;
+  getKnownWordMatchMode: () => NPlusOneMatchMode;
   tokenizeWithMecab: (text: string) => Promise<MergedToken[] | null>;
 }
 
@@ -41,6 +49,8 @@ export interface TokenizerDepsRuntimeOptions {
   setYomitanParserReadyPromise: (promise: Promise<void> | null) => void;
   getYomitanParserInitPromise: () => Promise<boolean> | null;
   setYomitanParserInitPromise: (promise: Promise<boolean> | null) => void;
+  isKnownWord: (text: string) => boolean;
+  getKnownWordMatchMode: () => NPlusOneMatchMode;
   getMecabTokenizer: () => MecabTokenizerLike | null;
 }
 
@@ -55,6 +65,8 @@ export function createTokenizerDepsRuntimeService(
     setYomitanParserReadyPromise: options.setYomitanParserReadyPromise,
     getYomitanParserInitPromise: options.getYomitanParserInitPromise,
     setYomitanParserInitPromise: options.setYomitanParserInitPromise,
+    isKnownWord: options.isKnownWord,
+    getKnownWordMatchMode: options.getKnownWordMatchMode,
     tokenizeWithMecab: async (text) => {
       const mecabTokenizer = options.getMecabTokenizer();
       if (!mecabTokenizer) {
@@ -64,11 +76,23 @@ export function createTokenizerDepsRuntimeService(
       if (!rawTokens || rawTokens.length === 0) {
         return null;
       }
-      return mergeTokens(rawTokens);
+      return mergeTokens(
+        rawTokens,
+        options.isKnownWord,
+        options.getKnownWordMatchMode(),
+      );
     },
   };
 }
 
+function resolveKnownWordText(
+  surface: string,
+  headword: string,
+  matchMode: NPlusOneMatchMode,
+): string {
+  return matchMode === "surface" ? surface : headword;
+}
+
 function extractYomitanHeadword(segment: YomitanParseSegment): string {
   const headwords = segment.headwords;
   if (!Array.isArray(headwords) || headwords.length === 0) {
@@ -86,6 +110,8 @@ function extractYomitanHeadword(segment: YomitanParseSegment): string {
 
 function mapYomitanParseResultsToMergedTokens(
   parseResults: unknown,
+  isKnownWord: (text: string) => boolean,
+  knownWordMatchMode: NPlusOneMatchMode,
 ): MergedToken[] | null {
   if (!Array.isArray(parseResults) || parseResults.length === 0) {
     return null;
@@ -161,6 +187,14 @@ function mapYomitanParseResultsToMergedTokens(
       endPos: end,
       partOfSpeech: PartOfSpeech.other,
       isMerged: true,
+      isKnown: (() => {
+        const matchText = resolveKnownWordText(
+          surface,
+          headword,
+          knownWordMatchMode,
+        );
+        return matchText ? isKnownWord(matchText) : false;
+      })(),
     });
   }
 
@@ -302,7 +336,11 @@ async function parseWithYomitanInternalParser(
       script,
       true,
     );
-    return mapYomitanParseResultsToMergedTokens(parseResults);
+    return mapYomitanParseResultsToMergedTokens(
+      parseResults,
+      deps.isKnownWord,
+      deps.getKnownWordMatchMode(),
+    );
   } catch (err) {
     console.error("Yomitan parser request failed:", (err as Error).message);
     return null;
diff --git a/src/main.ts b/src/main.ts
index 098d589..7a68cb6 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -89,7 +89,6 @@ import {
   applyMpvSubtitleRenderMetricsPatchService,
   broadcastRuntimeOptionsChangedRuntimeService,
   copyCurrentSubtitleService,
-  createAppLifecycleDepsRuntimeService,
   createOverlayManagerService,
   createFieldGroupingOverlayRuntimeService,
   createNumericShortcutRuntimeService,
@@ -128,7 +127,6 @@ import {
   shouldAutoInitializeOverlayRuntimeFromConfigService,
   shouldBindVisibleOverlayToMpvSubVisibilityService,
   showMpvOsdRuntimeService,
-  startAppLifecycleService,
   syncInvisibleOverlayMousePassthroughService,
   tokenizeSubtitleService,
   triggerFieldGroupingService,
@@ -137,13 +135,9 @@ import {
   updateLastCardFromClipboardService,
   updateVisibleOverlayVisibilityService,
 } from "./core/services";
-import {
-  runAppReadyRuntimeService,
-} from "./core/services/startup-service";
 import { applyRuntimeOptionResultRuntimeService } from "./core/services/runtime-options-ipc-service";
 import {
-  createAppLifecycleRuntimeDeps,
-  createAppReadyRuntimeDeps,
+  createAppReadyRuntimeRunner,
 } from "./main/app-lifecycle";
 import { handleMpvCommandFromIpcRuntime } from "./main/ipc-mpv-command";
 import {
@@ -158,6 +152,7 @@ import {
 import {
   runSubsyncManualFromIpcRuntime,
   triggerSubsyncFromConfigRuntime,
+  createSubsyncRuntimeServiceInputFromState,
 } from "./main/subsync-runtime";
 import {
   createOverlayModalRuntimeService,
@@ -171,6 +166,7 @@ import {
   createAppState,
 } from "./main/state";
 import { createStartupBootstrapRuntimeDeps } from "./main/startup";
+import { createAppLifecycleRuntimeRunner } from "./main/startup-lifecycle";
 import {
   ConfigService,
   DEFAULT_CONFIG,
@@ -562,130 +558,113 @@ const startupState = runStartupBootstrapRuntimeService(
       process.exitCode = 1;
       app.quit();
     },
-    startAppLifecycle: (args: CliArgs) => {
-      startAppLifecycleService(
-        args,
-        createAppLifecycleDepsRuntimeService(
-          createAppLifecycleRuntimeDeps({
-            app,
-            platform: process.platform,
-            shouldStartApp: (nextArgs: CliArgs) => shouldStartApp(nextArgs),
-            parseArgs: (argv: string[]) => parseArgs(argv),
-            handleCliCommand: (nextArgs: CliArgs, source: CliCommandSource) =>
-              handleCliCommand(nextArgs, source),
-            printHelp: () => printHelp(DEFAULT_TEXTHOOKER_PORT),
-            logNoRunningInstance: () => appLogger.logNoRunningInstance(),
-            onReady: async () => {
-              await runAppReadyRuntimeService(
-                createAppReadyRuntimeDeps({
-                  loadSubtitlePosition: () => loadSubtitlePosition(),
-                  resolveKeybindings: () => {
-                    appState.keybindings = resolveKeybindings(
-                      getResolvedConfig(),
-                      DEFAULT_KEYBINDINGS,
-                    );
-                  },
-                  createMpvClient: () => {
-                    appState.mpvClient = createMpvClientRuntimeService();
-                  },
-                  reloadConfig: () => {
-                    configService.reloadConfig();
-                    appLogger.logInfo(
-                      `Using config file: ${configService.getConfigPath()}`,
-                    );
-                  },
-                  getResolvedConfig: () => getResolvedConfig(),
-                  getConfigWarnings: () => configService.getWarnings(),
-                  logConfigWarning: (warning) => appLogger.logConfigWarning(warning),
-                  initRuntimeOptionsManager: () => {
-                    appState.runtimeOptionsManager = new RuntimeOptionsManager(
-                      () => configService.getConfig().ankiConnect,
-                      {
-                        applyAnkiPatch: (patch) => {
-                          if (appState.ankiIntegration) {
-                            appState.ankiIntegration.applyRuntimeConfigPatch(patch);
-                          }
-                        },
-                        onOptionsChanged: () => {
-                          broadcastRuntimeOptionsChanged();
-                          refreshOverlayShortcuts();
-                        },
-                      },
-                    );
-                  },
-                  setSecondarySubMode: (mode: SecondarySubMode) => {
-                    appState.secondarySubMode = mode;
-                  },
-                  defaultSecondarySubMode: "hover",
-                  defaultWebsocketPort: DEFAULT_CONFIG.websocket.port,
-                  hasMpvWebsocketPlugin: () => hasMpvWebsocketPlugin(),
-                  startSubtitleWebsocket: (port: number) => {
-                    subtitleWsService.start(port, () => appState.currentSubText);
-                  },
-                  log: (message) => appLogger.logInfo(message),
-                  createMecabTokenizerAndCheck: async () => {
-                    const tokenizer = new MecabTokenizer();
-                    appState.mecabTokenizer = tokenizer;
-                    await tokenizer.checkAvailability();
-                  },
-                  createSubtitleTimingTracker: () => {
-                    const tracker = new SubtitleTimingTracker();
-                    appState.subtitleTimingTracker = tracker;
-                  },
-                  loadYomitanExtension: async () => {
-                    await loadYomitanExtension();
-                  },
-                  texthookerOnlyMode: appState.texthookerOnlyMode,
-                  shouldAutoInitializeOverlayRuntimeFromConfig: () =>
-                    shouldAutoInitializeOverlayRuntimeFromConfig(),
-                  initializeOverlayRuntime: () => initializeOverlayRuntime(),
-                  handleInitialArgs: () => handleInitialArgs(),
-                }),
-              );
+    startAppLifecycle: createAppLifecycleRuntimeRunner({
+      app,
+      platform: process.platform,
+      shouldStartApp: (nextArgs: CliArgs) => shouldStartApp(nextArgs),
+      parseArgs: (argv: string[]) => parseArgs(argv),
+      handleCliCommand: (nextArgs: CliArgs, source: CliCommandSource) =>
+        handleCliCommand(nextArgs, source),
+      printHelp: () => printHelp(DEFAULT_TEXTHOOKER_PORT),
+      logNoRunningInstance: () => appLogger.logNoRunningInstance(),
+      onReady: createAppReadyRuntimeRunner({
+        loadSubtitlePosition: () => loadSubtitlePosition(),
+        resolveKeybindings: () => {
+          appState.keybindings = resolveKeybindings(
+            getResolvedConfig(),
+            DEFAULT_KEYBINDINGS,
+          );
+        },
+        createMpvClient: () => {
+          appState.mpvClient = createMpvClientRuntimeService();
+        },
+        reloadConfig: () => {
+          configService.reloadConfig();
+          appLogger.logInfo(`Using config file: ${configService.getConfigPath()}`);
+        },
+        getResolvedConfig: () => getResolvedConfig(),
+        getConfigWarnings: () => configService.getWarnings(),
+        logConfigWarning: (warning) => appLogger.logConfigWarning(warning),
+        initRuntimeOptionsManager: () => {
+          appState.runtimeOptionsManager = new RuntimeOptionsManager(
+            () => configService.getConfig().ankiConnect,
+            {
+              applyAnkiPatch: (patch) => {
+                if (appState.ankiIntegration) {
+                  appState.ankiIntegration.applyRuntimeConfigPatch(patch);
+                }
+              },
+              onOptionsChanged: () => {
+                broadcastRuntimeOptionsChanged();
+                refreshOverlayShortcuts();
+              },
             },
-            onWillQuitCleanup: () => {
-              restorePreviousSecondarySubVisibility();
-              globalShortcut.unregisterAll();
-              subtitleWsService.stop();
-              texthookerService.stop();
-              if (
-                appState.yomitanParserWindow &&
-                !appState.yomitanParserWindow.isDestroyed()
-              ) {
-                appState.yomitanParserWindow.destroy();
-              }
-              appState.yomitanParserWindow = null;
-              appState.yomitanParserReadyPromise = null;
-              appState.yomitanParserInitPromise = null;
-              if (appState.windowTracker) {
-                appState.windowTracker.stop();
-              }
-              if (appState.mpvClient && appState.mpvClient.socket) {
-                appState.mpvClient.socket.destroy();
-              }
-              if (appState.reconnectTimer) {
-                clearTimeout(appState.reconnectTimer);
-              }
-              if (appState.subtitleTimingTracker) {
-                appState.subtitleTimingTracker.destroy();
-              }
-              if (appState.ankiIntegration) {
-                appState.ankiIntegration.destroy();
-              }
-            },
-            shouldRestoreWindowsOnActivate: () =>
-              appState.overlayRuntimeInitialized &&
-              BrowserWindow.getAllWindows().length === 0,
-            restoreWindowsOnActivate: () => {
-              createMainWindow();
-              createInvisibleWindow();
-              updateVisibleOverlayVisibility();
-              updateInvisibleOverlayVisibility();
-            },
-          }),
-        ),
-      );
-    },
+          );
+        },
+        setSecondarySubMode: (mode: SecondarySubMode) => {
+          appState.secondarySubMode = mode;
+        },
+        defaultSecondarySubMode: "hover",
+        defaultWebsocketPort: DEFAULT_CONFIG.websocket.port,
+        hasMpvWebsocketPlugin: () => hasMpvWebsocketPlugin(),
+        startSubtitleWebsocket: (port: number) => {
+          subtitleWsService.start(port, () => appState.currentSubText);
+        },
+        log: (message) => appLogger.logInfo(message),
+        createMecabTokenizerAndCheck: async () => {
+          const tokenizer = new MecabTokenizer();
+          appState.mecabTokenizer = tokenizer;
+          await tokenizer.checkAvailability();
+        },
+        createSubtitleTimingTracker: () => {
+          const tracker = new SubtitleTimingTracker();
+          appState.subtitleTimingTracker = tracker;
+        },
+        loadYomitanExtension: async () => {
+          await loadYomitanExtension();
+        },
+        texthookerOnlyMode: appState.texthookerOnlyMode,
+        shouldAutoInitializeOverlayRuntimeFromConfig: () =>
+          shouldAutoInitializeOverlayRuntimeFromConfig(),
+        initializeOverlayRuntime: () => initializeOverlayRuntime(),
+        handleInitialArgs: () => handleInitialArgs(),
+      }),
+      onWillQuitCleanup: () => {
+        restorePreviousSecondarySubVisibility();
+        globalShortcut.unregisterAll();
+        subtitleWsService.stop();
+        texthookerService.stop();
+        if (appState.yomitanParserWindow && !appState.yomitanParserWindow.isDestroyed()) {
+          appState.yomitanParserWindow.destroy();
+        }
+        appState.yomitanParserWindow = null;
+        appState.yomitanParserReadyPromise = null;
+        appState.yomitanParserInitPromise = null;
+        if (appState.windowTracker) {
+          appState.windowTracker.stop();
+        }
+        if (appState.mpvClient && appState.mpvClient.socket) {
+          appState.mpvClient.socket.destroy();
+        }
+        if (appState.reconnectTimer) {
+          clearTimeout(appState.reconnectTimer);
+        }
+        if (appState.subtitleTimingTracker) {
+          appState.subtitleTimingTracker.destroy();
+        }
+        if (appState.ankiIntegration) {
+          appState.ankiIntegration.destroy();
+        }
+      },
+      shouldRestoreWindowsOnActivate: () =>
+        appState.overlayRuntimeInitialized && BrowserWindow.getAllWindows().length === 0,
+      restoreWindowsOnActivate: () => {
+        createMainWindow();
+        createInvisibleWindow();
+        updateVisibleOverlayVisibility();
+        updateInvisibleOverlayVisibility();
+      },
+    }),
   }),
 );
 
@@ -840,6 +819,11 @@ async function tokenizeSubtitle(text: string): Promise<SubtitleData> {
       setYomitanParserInitPromise: (promise) => {
         appState.yomitanParserInitPromise = promise;
       },
+      isKnownWord: (text) =>
+        Boolean(appState.ankiIntegration?.isKnownWord(text)),
+      getKnownWordMatchMode: () =>
+        appState.ankiIntegration?.getKnownWordMatchMode() ??
+        getResolvedConfig().ankiConnect.nPlusOne.matchMode,
       getMecabTokenizer: () => appState.mecabTokenizer,
     }),
   );
@@ -972,6 +956,8 @@ function initializeOverlayRuntime(): void {
       },
       showDesktopNotification,
       createFieldGroupingCallback: () => createFieldGroupingCallback(),
+      getKnownWordCacheStatePath: () =>
+        path.join(USER_DATA_PATH, "known-words-cache.json"),
     },
   );
   overlayManager.setInvisibleOverlayVisible(result.invisibleOverlayVisible);
@@ -1057,10 +1043,10 @@ const multiCopySession = numericShortcutRuntime.createSession();
 const mineSentenceSession = numericShortcutRuntime.createSession();
 
 function getSubsyncRuntimeServiceParams() {
-  return {
+  return createSubsyncRuntimeServiceInputFromState({
     getMpvClient: () => appState.mpvClient,
     getResolvedSubsyncConfig: () => getSubsyncConfig(getResolvedConfig().subsync),
-    isSubsyncInProgress: () => appState.subsyncInProgress,
+    getSubsyncInProgress: () => appState.subsyncInProgress,
     setSubsyncInProgress: (inProgress: boolean) => {
       appState.subsyncInProgress = inProgress;
     },
@@ -1070,7 +1056,7 @@ function getSubsyncRuntimeServiceParams() {
         restoreOnModalClose: "subsync",
       });
     },
-  };
+  });
 }
 
 async function triggerSubsyncFromConfig(): Promise<void> {
@@ -1336,7 +1322,7 @@ registerIpcRuntimeServices({
     openYomitanSettings: () => openYomitanSettings(),
     quitApp: () => app.quit(),
     toggleVisibleOverlay: () => toggleVisibleOverlay(),
-    tokenizeCurrentSubtitle: () => tokenizeCurrentSubtitle(appState.currentSubText),
+    tokenizeCurrentSubtitle: () => tokenizeSubtitle(appState.currentSubText),
     getCurrentSubtitleAss: () => appState.currentSubAssText,
     getMpvSubtitleRenderMetrics: () => appState.mpvSubtitleRenderMetrics,
     getSubtitlePosition: () => loadSubtitlePosition(),
@@ -1369,6 +1355,8 @@ registerIpcRuntimeServices({
     setAnkiIntegration: (integration: AnkiIntegration | null) => {
       appState.ankiIntegration = integration;
     },
+    getKnownWordCacheStatePath: () =>
+      path.join(USER_DATA_PATH, "known-words-cache.json"),
     showDesktopNotification,
     createFieldGroupingCallback: () => createFieldGroupingCallback(),
     broadcastRuntimeOptionsChanged: () => broadcastRuntimeOptionsChanged(),
diff --git a/src/main/app-lifecycle.ts b/src/main/app-lifecycle.ts
index 19a18cb..b1ef3a8 100644
--- a/src/main/app-lifecycle.ts
+++ b/src/main/app-lifecycle.ts
@@ -87,3 +87,11 @@ export function createAppReadyRuntimeDeps(
     handleInitialArgs: params.handleInitialArgs,
   };
 }
+
+export function createAppReadyRuntimeRunner(
+  params: AppReadyRuntimeDepsFactoryInput,
+): () => Promise<void> {
+  return async () => {
+    await runAppReadyRuntimeService(createAppReadyRuntimeDeps(params));
+  };
+}
diff --git a/src/main/dependencies.ts b/src/main/dependencies.ts
index c092110..3313192 100644
--- a/src/main/dependencies.ts
+++ b/src/main/dependencies.ts
@@ -98,6 +98,7 @@ export interface AnkiJimakuIpcRuntimeServiceDepsParams {
   getMpvClient: AnkiJimakuIpcRuntimeOptions["getMpvClient"];
   getAnkiIntegration: AnkiJimakuIpcRuntimeOptions["getAnkiIntegration"];
   setAnkiIntegration: AnkiJimakuIpcRuntimeOptions["setAnkiIntegration"];
+  getKnownWordCacheStatePath: AnkiJimakuIpcRuntimeOptions["getKnownWordCacheStatePath"];
   showDesktopNotification: AnkiJimakuIpcRuntimeOptions["showDesktopNotification"];
   createFieldGroupingCallback: AnkiJimakuIpcRuntimeOptions["createFieldGroupingCallback"];
   broadcastRuntimeOptionsChanged: AnkiJimakuIpcRuntimeOptions["broadcastRuntimeOptionsChanged"];
@@ -224,6 +225,7 @@ export function createAnkiJimakuIpcRuntimeServiceDeps(
     getMpvClient: params.getMpvClient,
     getAnkiIntegration: params.getAnkiIntegration,
     setAnkiIntegration: params.setAnkiIntegration,
+    getKnownWordCacheStatePath: params.getKnownWordCacheStatePath,
     showDesktopNotification: params.showDesktopNotification,
     createFieldGroupingCallback: params.createFieldGroupingCallback,
     broadcastRuntimeOptionsChanged: params.broadcastRuntimeOptionsChanged,
diff --git a/src/main/startup-lifecycle.ts b/src/main/startup-lifecycle.ts
new file mode 100644
index 0000000..ac5a744
--- /dev/null
+++ b/src/main/startup-lifecycle.ts
@@ -0,0 +1,44 @@
+import { CliArgs, CliCommandSource } from "../cli/args";
+import { createAppLifecycleDepsRuntimeService } from "../core/services";
+import { startAppLifecycleService } from "../core/services/app-lifecycle-service";
+import type { AppLifecycleDepsRuntimeOptions } from "../core/services/app-lifecycle-service";
+import { createAppLifecycleRuntimeDeps } from "./app-lifecycle";
+
+export interface AppLifecycleRuntimeRunnerParams {
+  app: AppLifecycleDepsRuntimeOptions["app"];
+  platform: NodeJS.Platform;
+  shouldStartApp: (args: CliArgs) => boolean;
+  parseArgs: (argv: string[]) => CliArgs;
+  handleCliCommand: (nextArgs: CliArgs, source: CliCommandSource) => void;
+  printHelp: () => void;
+  logNoRunningInstance: () => void;
+  onReady: () => Promise<void>;
+  onWillQuitCleanup: () => void;
+  shouldRestoreWindowsOnActivate: () => boolean;
+  restoreWindowsOnActivate: () => void;
+}
+
+export function createAppLifecycleRuntimeRunner(
+  params: AppLifecycleRuntimeRunnerParams,
+): (args: CliArgs) => void {
+  return (args: CliArgs): void => {
+    startAppLifecycleService(
+      args,
+      createAppLifecycleDepsRuntimeService(
+        createAppLifecycleRuntimeDeps({
+          app: params.app,
+          platform: params.platform,
+          shouldStartApp: params.shouldStartApp,
+          parseArgs: params.parseArgs,
+          handleCliCommand: params.handleCliCommand,
+          printHelp: params.printHelp,
+          logNoRunningInstance: params.logNoRunningInstance,
+          onReady: params.onReady,
+          onWillQuitCleanup: params.onWillQuitCleanup,
+          shouldRestoreWindowsOnActivate: params.shouldRestoreWindowsOnActivate,
+          restoreWindowsOnActivate: params.restoreWindowsOnActivate,
+        }),
+      ),
+    );
+  };
+}
diff --git a/src/main/subsync-runtime.ts b/src/main/subsync-runtime.ts
index f6fb746..4163e26 100644
--- a/src/main/subsync-runtime.ts
+++ b/src/main/subsync-runtime.ts
@@ -13,6 +13,28 @@ export interface SubsyncRuntimeServiceInput {
   openManualPicker: (payload: SubsyncManualPayload) => void;
 }
 
+export interface SubsyncRuntimeServiceStateInput {
+  getMpvClient: SubsyncRuntimeServiceInput["getMpvClient"];
+  getResolvedSubsyncConfig: SubsyncRuntimeServiceInput["getResolvedSubsyncConfig"];
+  getSubsyncInProgress: () => boolean;
+  setSubsyncInProgress: SubsyncRuntimeServiceInput["setSubsyncInProgress"];
+  showMpvOsd: SubsyncRuntimeServiceInput["showMpvOsd"];
+  openManualPicker: SubsyncRuntimeServiceInput["openManualPicker"];
+}
+
+export function createSubsyncRuntimeServiceInputFromState(
+  input: SubsyncRuntimeServiceStateInput,
+): SubsyncRuntimeServiceInput {
+  return {
+    getMpvClient: input.getMpvClient,
+    getResolvedSubsyncConfig: input.getResolvedSubsyncConfig,
+    isSubsyncInProgress: input.getSubsyncInProgress,
+    setSubsyncInProgress: input.setSubsyncInProgress,
+    showMpvOsd: input.showMpvOsd,
+    openManualPicker: input.openManualPicker,
+  };
+}
+
 export function createSubsyncRuntimeServiceDeps(
   params: SubsyncRuntimeServiceInput,
 ): SubsyncRuntimeDeps {
diff --git a/src/renderer/style.css b/src/renderer/style.css
index 5c699ac..b95fdf2 100644
--- a/src/renderer/style.css
+++ b/src/renderer/style.css
@@ -284,6 +284,11 @@ body.settings-modal-open #subtitleContainer {
   position: relative;
 }
 
+#subtitleRoot .word.word-known {
+  color: #a6da95;
+  text-shadow: 0 0 6px rgba(166, 218, 149, 0.35);
+}
+
 #subtitleRoot .word:hover {
   background: rgba(255, 255, 255, 0.2);
   border-radius: 3px;
diff --git a/src/renderer/subtitle-render.ts b/src/renderer/subtitle-render.ts
index d28b7ad..e26ae2f 100644
--- a/src/renderer/subtitle-render.ts
+++ b/src/renderer/subtitle-render.ts
@@ -26,7 +26,7 @@ function renderWithTokens(root: HTMLElement, tokens: MergedToken[]): void {
       for (let i = 0; i < parts.length; i += 1) {
         if (parts[i]) {
           const span = document.createElement("span");
-          span.className = "word";
+          span.className = token.isKnown ? "word word-known" : "word";
           span.textContent = parts[i];
           if (token.reading) span.dataset.reading = token.reading;
           if (token.headword) span.dataset.headword = token.headword;
@@ -40,7 +40,7 @@ function renderWithTokens(root: HTMLElement, tokens: MergedToken[]): void {
     }
 
     const span = document.createElement("span");
-    span.className = "word";
+    span.className = token.isKnown ? "word word-known" : "word";
     span.textContent = surface;
     if (token.reading) span.dataset.reading = token.reading;
     if (token.headword) span.dataset.headword = token.headword;
diff --git a/src/token-merger.ts b/src/token-merger.ts
index 9c38be9..040f747 100644
--- a/src/token-merger.ts
+++ b/src/token-merger.ts
@@ -179,7 +179,11 @@ export function shouldMerge(lastStandaloneToken: Token, token: Token): boolean {
   return false;
 }
 
-export function mergeTokens(tokens: Token[]): MergedToken[] {
+export function mergeTokens(
+  tokens: Token[],
+  isKnownWord: (text: string) => boolean = () => false,
+  knownWordMatchMode: "headword" | "surface" = "headword",
+): MergedToken[] {
   if (!tokens || tokens.length === 0) {
     return [];
   }
@@ -205,6 +209,13 @@ export function mergeTokens(tokens: Token[]): MergedToken[] {
 
     if (shouldMergeToken && result.length > 0) {
       const prev = result.pop()!;
+      const mergedHeadword = prev.headword;
+      const headwordForKnownMatch = (() => {
+        if (knownWordMatchMode === "surface") {
+          return prev.surface;
+        }
+        return mergedHeadword;
+      })();
       result.push({
         surface: prev.surface + token.word,
         reading: prev.reading + tokenReading,
@@ -213,8 +224,17 @@ export function mergeTokens(tokens: Token[]): MergedToken[] {
         endPos: end,
         partOfSpeech: prev.partOfSpeech,
         isMerged: true,
+        isKnown: headwordForKnownMatch
+          ? isKnownWord(headwordForKnownMatch)
+          : false,
       });
     } else {
+      const headwordForKnownMatch = (() => {
+        if (knownWordMatchMode === "surface") {
+          return token.word;
+        }
+        return token.headword;
+      })();
       result.push({
         surface: token.word,
         reading: tokenReading,
@@ -223,6 +243,9 @@ export function mergeTokens(tokens: Token[]): MergedToken[] {
         endPos: end,
         partOfSpeech: token.partOfSpeech,
         isMerged: false,
+        isKnown: headwordForKnownMatch
+          ? isKnownWord(headwordForKnownMatch)
+          : false,
       });
     }
 
diff --git a/src/types.ts b/src/types.ts
index 2eff3b3..381c5f8 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -49,6 +49,7 @@ export interface MergedToken {
   endPos: number;
   partOfSpeech: PartOfSpeech;
   isMerged: boolean;
+  isKnown: boolean;
 }
 
 export interface WindowGeometry {
@@ -150,7 +151,8 @@ export interface KikuMergePreviewResponse {
 
 export type RuntimeOptionId =
   | "anki.autoUpdateNewCards"
-  | "anki.kikuFieldGrouping";
+  | "anki.kikuFieldGrouping"
+  | "anki.nPlusOneMatchMode";
 
 export type RuntimeOptionScope = "ankiConnect";
 
@@ -158,6 +160,8 @@ export type RuntimeOptionValueType = "boolean" | "enum";
 
 export type RuntimeOptionValue = boolean | string;
 
+export type NPlusOneMatchMode = "headword" | "surface";
+
 export interface RuntimeOptionState {
   id: RuntimeOptionId;
   label: string;
@@ -221,14 +225,20 @@ export interface AnkiConnectConfig {
     fallbackDuration?: number;
     maxMediaDuration?: number;
   };
-  behavior?: {
-    overwriteAudio?: boolean;
-    overwriteImage?: boolean;
-    mediaInsertMode?: "append" | "prepend";
-    highlightWord?: boolean;
-    notificationType?: "osd" | "system" | "both" | "none";
-    autoUpdateNewCards?: boolean;
+  nPlusOne?: {
+    highlightEnabled?: boolean;
+    refreshMinutes?: number;
+    matchMode?: NPlusOneMatchMode;
+    decks?: string[];
   };
+  behavior?: {
+      overwriteAudio?: boolean;
+      overwriteImage?: boolean;
+      mediaInsertMode?: "append" | "prepend";
+      highlightWord?: boolean;
+      notificationType?: "osd" | "system" | "both" | "none";
+      autoUpdateNewCards?: boolean;
+    };
   metadata?: {
     pattern?: string;
   };
@@ -363,6 +373,12 @@ export interface ResolvedConfig {
       fallbackDuration: number;
       maxMediaDuration: number;
     };
+    nPlusOne: {
+      highlightEnabled: boolean;
+      refreshMinutes: number;
+      matchMode: NPlusOneMatchMode;
+      decks: string[];
+    };
     behavior: {
       overwriteAudio: boolean;
       overwriteImage: boolean;